版本：2.3.x

快速开始

CnosDB SQL 的灵感来自于 DataFusion，我们支持DataFusion的大部分SQL语法。

注意：为了查询能更高效，没有指定排序的查询，每次行顺序都不一定相同，如果需要按字段排序的话，请参看ORDER BY子句。

示例数据

为了进一步学习CnosDB，本节将提供示例数据供您下载，并教您如何将数据导入数据库。后面章节中引用的数据源都来自此示例数据。

下载数据

如果在 cnosdb-cli 中，请输入\q退出

在shell中执行以下命令将在本地生成一个名称为oceanic_station的Line Protocol格式的数据文件

curl -o oceanic_station.txt https://dl.cnosdb.com/sample/oceanic_station.txt

导入数据

启动CLI
```
cnosdb-cli
```
创建数据库
```
create database oceanic_station;
```
切换到指定数据库
```
\c oceanic_station
```
导入数据
执行\w指令，\w后面为数据文件的绝对路径或相对cnosdb-cli的工作路径。
```
\w oceanic_station.txt
```

语法

[ WITH with_query [, ...] ]
SELECT [ ALL | DISTINCT ] select_expression [, ...]
    [ FROM from_item [, ...] ]
    [ WHERE condition ]
    [ GROUP BY [ ALL | DISTINCT ] grouping_element [, ...] ]
    [ HAVING condition ]
    [ { UNION | INTERSECT | EXCEPT } [ ALL | DISTINCT ] select ]
    [ ORDER BY expression [ ASC | DESC ] [, ...] ]
    [ OFFSET count ]
    [ LIMIT { count | ALL } ];

-- from_item
-- 1.
    tb_name [ [ AS ] alias [ ( column_alias [, ...] ) ] ]
-- 2.
    from_item join_type from_item
    { ON join_condition | USING ( join_column [, ...] ) }

-- join_type
    [ INNER ] JOIN
    LEFT [ OUTER ] JOIN
    RIGHT [ OUTER ] JOIN
    FULL [ OUTER ] JOIN
    CROSS JOIN

-- grouping_element
    ()

SELECT 子句

SELECT *

通配符 * 可以用于代指全部列。

示例

SELECT * FROM air;

+---------------------+-------------+------------+-------------+----------+
| time                | station     | visibility | temperature | pressure |
+---------------------+-------------+------------+-------------+----------+
| 2022-01-28 13:21:00 | XiaoMaiDao  | 56         | 69          | 77       |
| 2022-01-28 13:24:00 | XiaoMaiDao  | 50         | 78          | 66       |
| 2022-01-28 13:27:00 | XiaoMaiDao  | 67         | 62          | 59       |
| 2022-01-28 13:30:00 | XiaoMaiDao  | 65         | 79          | 77       |
| 2022-01-28 13:33:00 | XiaoMaiDao  | 53         | 53          | 68       |
| 2022-01-28 13:36:00 | XiaoMaiDao  | 74         | 72          | 68       |
| 2022-01-28 13:39:00 | XiaoMaiDao  | 71         | 71          | 80       |
| 2022-01-28 13:21:00 | LianYunGang | 78         | 69          | 71       |
| 2022-01-28 13:24:00 | LianYunGang | 79         | 80          | 51       |
| 2022-01-28 13:27:00 | LianYunGang | 59         | 74          | 59       |
| 2022-01-28 13:30:00 | LianYunGang | 67         | 70          | 72       |
| 2022-01-28 13:33:00 | LianYunGang | 80         | 70          | 68       |
| 2022-01-28 13:36:00 | LianYunGang | 59         | 70          | 54       |
+---------------------+-------------+------------+-------------+----------+

ALL/DISTINCT

语法

SELECT [ ALL | DISTINCT ] select_expression [, ...];

在SELECT关键字后可以使用DISTINCT去掉重复字段，只返回去重后的值。使用ALL会返回字段中所有重复的值。不指定此选项时，默认值为ALL。

示例

SELECT DISTINCT station, visibility FROM air;

+-------------+------------+
| station     | visibility |
+-------------+------------+
| XiaoMaiDao  | 56         |
| XiaoMaiDao  | 50         |
| XiaoMaiDao  | 67         |
| XiaoMaiDao  | 65         |
| XiaoMaiDao  | 53         |
| XiaoMaiDao  | 74         |
| XiaoMaiDao  | 71         |
| LianYunGang | 78         |
| LianYunGang | 79         |
| LianYunGang | 59         |
| LianYunGang | 67         |
| LianYunGang | 80         |
+-------------+------------+

SELECT station, visibility FROM air;

+-------------+------------+
| station     | visibility |
+-------------+------------+
| XiaoMaiDao  | 56         |
| XiaoMaiDao  | 50         |
| XiaoMaiDao  | 67         |
| XiaoMaiDao  | 65         |
| XiaoMaiDao  | 53         |
| XiaoMaiDao  | 74         |
| XiaoMaiDao  | 71         |
| LianYunGang | 78         |
| LianYunGang | 79         |
| LianYunGang | 59         |
| LianYunGang | 67         |
| LianYunGang | 80         |
| LianYunGang | 59         |
+-------------+------------+

别名

可以用AS关键字为列表达式或表取别名

为列表达式取别名

语法

expression [ [ AS ] column_alias ]

示例

SELECT station s, visibility AS v FROM air;

+-------------+----+
| s           | v  |
+-------------+----+
| XiaoMaiDao  | 56 |
| XiaoMaiDao  | 50 |
| XiaoMaiDao  | 67 |
| XiaoMaiDao  | 65 |
| XiaoMaiDao  | 53 |
| XiaoMaiDao  | 74 |
| XiaoMaiDao  | 71 |
| LianYunGang | 78 |
| LianYunGang | 79 |
| LianYunGang | 59 |
| LianYunGang | 67 |
| LianYunGang | 80 |
| LianYunGang | 59 |
+-------------+----+

为表取别名

你也可以用关键字AS为表取别名。

语法

FROM tb_name [AS] alias_name

示例

SELECT a.visibility, s.temperature
FROM air AS a JOIN sea s ON a.temperature = s.temperature limit 10;

+------------+-------------+
| visibility | temperature |
+------------+-------------+
| 80.0       | 56.0        |
| 57.0       | 56.0        |
| 70.0       | 56.0        |
| 78.0       | 56.0        |
| 56.0       | 56.0        |
| 63.0       | 56.0        |
| 69.0       | 56.0        |
| 59.0       | 56.0        |
| 60.0       | 56.0        |
| 51.0       | 56.0        |
+------------+-------------+

SELECT限制

如果SELECT子句仅包含Tag列，相当于 SELECT DISTINCT Tag列

示例

-- station是Tag列，temperature是Field列
SELECT station, temperature FROM air;

+-------------+-------------+
| station     | temperature |
+-------------+-------------+
| XiaoMaiDao  | 69          |
| XiaoMaiDao  | 78          |
| XiaoMaiDao  | 62          |
| XiaoMaiDao  | 79          |
| XiaoMaiDao  | 53          |
| XiaoMaiDao  | 72          |
| XiaoMaiDao  | 71          |
| LianYunGang | 69          |
| LianYunGang | 80          |
| LianYunGang | 74          |
| LianYunGang | 70          |
| LianYunGang | 70          |
| LianYunGang | 70          |
+-------------+-------------+

-- station 是Tag列
SELECT station FROM air;

+-------------+
| station     |
+-------------+
| XiaoMaiDao  |
| LianYunGang |
+-------------+ 

LIMIT 子句

语法

LIMIT n

限制返回结果集的行数为n，n必须非负。

示例

SELECT *
FROM air LIMIT 10;

+---------------------+-------------+------------+-------------+----------+
| time                | station     | visibility | temperature | pressure |
+---------------------+-------------+------------+-------------+----------+
| 2022-01-28 13:21:00 | XiaoMaiDao  | 56         | 69          | 77       |
| 2022-01-28 13:24:00 | XiaoMaiDao  | 50         | 78          | 66       |
| 2022-01-28 13:27:00 | XiaoMaiDao  | 67         | 62          | 59       |
| 2022-01-28 13:30:00 | XiaoMaiDao  | 65         | 79          | 77       |
| 2022-01-28 13:33:00 | XiaoMaiDao  | 53         | 53          | 68       |
| 2022-01-28 13:36:00 | XiaoMaiDao  | 74         | 72          | 68       |
| 2022-01-28 13:39:00 | XiaoMaiDao  | 71         | 71          | 80       |
| 2022-01-28 13:21:00 | LianYunGang | 78         | 69          | 71       |
| 2022-01-28 13:24:00 | LianYunGang | 79         | 80          | 51       |
| 2022-01-28 13:27:00 | LianYunGang | 59         | 74          | 59       |
+---------------------+-------------+------------+-------------+----------+

OFFSET 子句

语法

OFFSET m

返回的结果集跳过 m 条记录, 默认 m=0。示例

SELECT *
FROM air OFFSET 10;

+---------------------+-------------+------------+-------------+----------+
| time                | station     | visibility | temperature | pressure |
+---------------------+-------------+------------+-------------+----------+
| 2022-01-28 13:30:00 | LianYunGang | 67         | 70          | 72       |
| 2022-01-28 13:33:00 | LianYunGang | 80         | 70          | 68       |
| 2022-01-28 13:36:00 | LianYunGang | 59         | 70          | 54       |
+---------------------+-------------+------------+-------------+----------+

OFFSET可以和LIMIT语句配合使用，用于指定跳过的行数，格式为LIMIT n OFFSET m。其中：LIMIT n控制输出n行数据，OFFSET m表示在开始返回数据之前跳过的行数。 OFFSET 0与省略OFFSET子句效果相同。

示例

SELECT *
FROM air LIMIT 3 OFFSET 3;

+---------------------+------------+------------+-------------+----------+
| time                | station    | visibility | temperature | pressure |
+---------------------+------------+------------+-------------+----------+
| 2022-01-28 13:30:00 | XiaoMaiDao | 65         | 79          | 77       |
| 2022-01-28 13:33:00 | XiaoMaiDao | 53         | 53          | 68       |
| 2022-01-28 13:36:00 | XiaoMaiDao | 74         | 72          | 68       |
+---------------------+------------+------------+-------------+----------+

WITH 子句

语法

WITH cte AS cte_query_definiton [, ...] query

可选。WITH子句包含一个或多个常用的表达式CTE(Common Table Expression)。 CTE充当当前运行环境中的临时表，您可以在之后的查询中引用该表。CTE使用规则如下：

在同一WITH子句中的CTE必须具有唯一的名字。
在WITH子句中定义的CTE仅对在其后定义的同一WITH子句中的其他CTE可以使用。假设A是子句中的第一个CTE，B是子句中的第二个CTE：

示例

SELECT station, avg 
FROM (  SELECT station, AVG(visibility) AS avg 
        FROM air 
        GROUP BY station) AS x;

+-------------+--------------------+
| station     | avg                |
+-------------+--------------------+
| XiaoMaiDao  | 62.285714285714285 |
| LianYunGang | 70.33333333333333  |
+-------------+--------------------+

WITH x AS 
    (SELECT station, AVG(visibility) AS avg FROM air GROUP BY station)
SELECT station, avg
FROM x;

+-------------+--------------------+
| station     | avg                |
+-------------+--------------------+
| XiaoMaiDao  | 62.285714285714285 |
| LianYunGang | 70.33333333333333  |
+-------------+--------------------+

UNION 子句

UNION 子句用于合并多个 SELECT 语句的分析结果。

语法

select_clause_set_left
[ UNION | UNION ALL| EXCEPT | INTERSECT]
select_clause_set_right
[sort_list_columns] [limit_clause]

UNION会对合并的结果集去重， UNION ALL保留合并的结果集中相同的数据 EXCEPT 会作两个结果集的差，从左查询中返回右查询没有找到的所有非重复值 INTERSECT 返回两个结果集的交集（即两个查询都返回的所有非重复值）。

注意

UNION 内每个 SELECT 子句必须拥有相同数量的列，对应列的数据类型相同。

示例

UNION ALL

SELECT visibility FROM air WHERE temperature < 60
UNION ALL
SELECT visibility FROM air WHERE temperature > 50 LIMIT 10;

+------------+
| visibility |
+------------+
| 53         |
| 56         |
| 50         |
| 67         |
| 65         |
| 53         |
| 74         |
| 71         |
| 78         |
| 79         |
+------------+

UNION

SELECT visibility FROM air WHERE temperature < 60
UNION
SELECT visibility FROM air WHERE temperature > 50 LIMIT 10;

+------------+
| visibility |
+------------+
| 53         |
| 56         |
| 50         |
| 67         |
| 65         |
| 74         |
| 71         |
| 78         |
| 79         |
| 59         |
+------------+

EXCEPT

SELECT visibility FROM air
EXCEPT
SELECT visibility FROM air WHERE temperature < 50 LIMIT 10;

+------------+
| visibility |
+------------+
| 56         |
| 50         |
| 67         |
| 65         |
| 53         |
| 74         |
| 71         |
| 78         |
| 79         |
| 59         |
+------------+

INTERSECT

SELECT visibility FROM air
INTERSECT
SELECT visibility FROM air WHERE temperature > 50 LIMIT 10;

+------------+
| visibility |
+------------+
| 56         |
| 50         |
| 67         |
| 65         |
| 53         |
| 74         |
| 71         |
| 78         |
| 79         |
| 59         |
+------------+

ORDER BY 子句

按引用的表达式对结果进行排序。默认情况使用升序 (ASC)。通过在 ORDER BY 的表达式后添加 DESC 按降序排序。

示例

SELECT * FROM air ORDER BY temperature;

+---------------------+-------------+------------+-------------+----------+
| time                | station     | visibility | temperature | pressure |
+---------------------+-------------+------------+-------------+----------+
| 2022-01-28 13:33:00 | XiaoMaiDao  | 53         | 53          | 68       |
| 2022-01-28 13:27:00 | XiaoMaiDao  | 67         | 62          | 59       |
| 2022-01-28 13:21:00 | XiaoMaiDao  | 56         | 69          | 77       |
| 2022-01-28 13:21:00 | LianYunGang | 78         | 69          | 71       |
| 2022-01-28 13:30:00 | LianYunGang | 67         | 70          | 72       |
| 2022-01-28 13:33:00 | LianYunGang | 80         | 70          | 68       |
| 2022-01-28 13:36:00 | LianYunGang | 59         | 70          | 54       |
| 2022-01-28 13:39:00 | XiaoMaiDao  | 71         | 71          | 80       |
| 2022-01-28 13:36:00 | XiaoMaiDao  | 74         | 72          | 68       |
| 2022-01-28 13:27:00 | LianYunGang | 59         | 74          | 59       |
| 2022-01-28 13:24:00 | XiaoMaiDao  | 50         | 78          | 66       |
| 2022-01-28 13:30:00 | XiaoMaiDao  | 65         | 79          | 77       |
| 2022-01-28 13:24:00 | LianYunGang | 79         | 80          | 51       |
+---------------------+-------------+------------+-------------+----------+

SELECT * FROM air ORDER BY temperature DESC;

+---------------------+-------------+------------+-------------+----------+
| time                | station     | visibility | temperature | pressure |
+---------------------+-------------+------------+-------------+----------+
| 2022-01-28 13:24:00 | LianYunGang | 79         | 80          | 51       |
| 2022-01-28 13:30:00 | XiaoMaiDao  | 65         | 79          | 77       |
| 2022-01-28 13:24:00 | XiaoMaiDao  | 50         | 78          | 66       |
| 2022-01-28 13:27:00 | LianYunGang | 59         | 74          | 59       |
| 2022-01-28 13:36:00 | XiaoMaiDao  | 74         | 72          | 68       |
| 2022-01-28 13:39:00 | XiaoMaiDao  | 71         | 71          | 80       |
| 2022-01-28 13:30:00 | LianYunGang | 67         | 70          | 72       |
| 2022-01-28 13:33:00 | LianYunGang | 80         | 70          | 68       |
| 2022-01-28 13:36:00 | LianYunGang | 59         | 70          | 54       |
| 2022-01-28 13:21:00 | XiaoMaiDao  | 56         | 69          | 77       |
| 2022-01-28 13:21:00 | LianYunGang | 78         | 69          | 71       |
| 2022-01-28 13:27:00 | XiaoMaiDao  | 67         | 62          | 59       |
| 2022-01-28 13:33:00 | XiaoMaiDao  | 53         | 53          | 68       |
+---------------------+-------------+------------+-------------+----------+

SELECT * FROM air ORDER BY station, temperature;

+---------------------+-------------+------------+-------------+----------+
| time                | station     | visibility | temperature | pressure |
+---------------------+-------------+------------+-------------+----------+
| 2022-01-28 13:21:00 | LianYunGang | 78         | 69          | 71       |
| 2022-01-28 13:30:00 | LianYunGang | 67         | 70          | 72       |
| 2022-01-28 13:33:00 | LianYunGang | 80         | 70          | 68       |
| 2022-01-28 13:36:00 | LianYunGang | 59         | 70          | 54       |
| 2022-01-28 13:27:00 | LianYunGang | 59         | 74          | 59       |
| 2022-01-28 13:24:00 | LianYunGang | 79         | 80          | 51       |
| 2022-01-28 13:33:00 | XiaoMaiDao  | 53         | 53          | 68       |
| 2022-01-28 13:27:00 | XiaoMaiDao  | 67         | 62          | 59       |
| 2022-01-28 13:21:00 | XiaoMaiDao  | 56         | 69          | 77       |
| 2022-01-28 13:39:00 | XiaoMaiDao  | 71         | 71          | 80       |
| 2022-01-28 13:36:00 | XiaoMaiDao  | 74         | 72          | 68       |
| 2022-01-28 13:24:00 | XiaoMaiDao  | 50         | 78          | 66       |
| 2022-01-28 13:30:00 | XiaoMaiDao  | 65         | 79          | 77       |
+---------------------+-------------+------------+-------------+----------+

IN

IN 操作符允许您在 WHERE 子句中规定多个值。

示例

SELECT station, temperature, visibility FROM air WHERE temperature  IN (68, 69);

+-------------+-------------+------------+
| station     | temperature | visibility |
+-------------+-------------+------------+
| XiaoMaiDao  | 69          | 56         |
| LianYunGang | 69          | 78         |
+-------------+-------------+------------+

注意

IN 列表暂不支持表达式，暂时只支持常量

SHOW

语法

SHOW {DATABASES | TABLES | QUERIES}

显示所有数据库，或显示所有表, 或正在执行的SQL

示例

SHOW DATABASES;

+----------+
| Database |
+----------+
| public   |
+----------+

SHOW TABLES;

+-------+
| Table |
+-------+
| sea   |
| air   |
| wind  |
+-------+

SHOW QUERIES;

+----------+------------------------------------------------------------------+-----------------------------------------+-----------+----------------------------------------+-------------+------------+--------------+
| query_id | query_text                                                       | user_id                                 | user_name | tenant_id                              | tenant_name | state      | duration     |
+----------+------------------------------------------------------------------+-----------------------------------------+-----------+----------------------------------------+-------------+------------+--------------+
| 36       | select * FROM air join sea ON air.temperature = sea.temperature; | 108709109615072923019194003831375742761 | root      | 13215126763611749424716665303609634152 | cnosdb      | SCHEDULING | 12.693345666 |
+----------+------------------------------------------------------------------+-----------------------------------------+-----------+----------------------------------------+-------------+------------+--------------+

关于 SHOW QUERIES 语句的详细信息，可以在系统表 QUERIES 查看

EXPLAIN

语法

EXPLAIN [ ANALYZE ] [ VERBOSE ] <statement>;

说明

EXPLAIN 语句仅用于显示查询的执行计划，而不执行查询。

EXPLAIN ANALYZE 执行查询，并显示查询的执行计划。

EXPLAIN ANALYZE VERBOSE 执行查询，并显示更详细的执行计划，包括读取的行数等。

示例

EXPLAIN SELECT station, temperature, visibility FROM air;

+---------------+-----------------------------------------------------------------------------------------------------------------------------+
| plan_type     | plan                                                                                                                        |
+---------------+-----------------------------------------------------------------------------------------------------------------------------+
| logical_plan  | Projection: #air.station, #air.temperature, #air.visibility                                                                 |
|               |   TableScan: air projection=[station, visibility, temperature]                                                              |
| physical_plan | ProjectionExec: expr=[station@0 as station, temperature@2 as temperature, visibility@1 as visibility]                       |
|               |   TskvExec: limit=None, predicate=ColumnDomains { column_to_domain: Some({}) }, projection=[station,visibility,temperature] |
|               |                                                                                                                             |
+---------------+-----------------------------------------------------------------------------------------------------------------------------+

EXPLAIN ANALYZE SELECT station, temperature, visibility FROM air;

+-------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| plan_type         | plan                                                                                                                                                                                                                                                                                                                                    |
+-------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Plan with Metrics | ProjectionExec: expr=[station@0 as station, temperature@2 as temperature, visibility@1 as visibility], metrics=[output_rows=13, elapsed_compute=20.375µs, spill_count=0, spilled_bytes=0, mem_used=0]                                                                                                                                   |
|                   |   TskvExec: limit=None, predicate=ColumnDomains { column_to_domain: Some({}) }, projection=[station,visibility,temperature], metrics=[output_rows=13, elapsed_compute=15.929624ms, spill_count=0, spilled_bytes=0, mem_used=0, elapsed_series_scan=1.698791ms, elapsed_point_to_record_batch=4.572954ms, elapsed_field_scan=5.119076ms] |
|                   |                                                                                                                                                                                                                                                                                                                                         |
+-------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

EXPLAIN ANALYZE SELECT station, temperature, visibility FROM air;

+-------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| plan_type         | plan                                                                                                                                                                                                                                                                                                                                    |
+-------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Plan with Metrics | ProjectionExec: expr=[station@0 as station, temperature@2 as temperature, visibility@1 as visibility], metrics=[output_rows=13, elapsed_compute=20.375µs, spill_count=0, spilled_bytes=0, mem_used=0]                                                                                                                                   |
|                   |   TskvExec: limit=None, predicate=ColumnDomains { column_to_domain: Some({}) }, projection=[station,visibility,temperature], metrics=[output_rows=13, elapsed_compute=15.929624ms, spill_count=0, spilled_bytes=0, mem_used=0, elapsed_series_scan=1.698791ms, elapsed_point_to_record_batch=4.572954ms, elapsed_field_scan=5.119076ms] |
|                   |                                                                                                                                                                                                                                                                                                                                         |
+-------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

EXPLAIN ANALYZE VERBOSE SELECT station, temperature, visibility FROM air;

+------------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| plan_type              | plan                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
+------------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Plan with Metrics      | ProjectionExec: expr=[station@0 as station, temperature@2 as temperature, visibility@1 as visibility], metrics=[output_rows=13, elapsed_compute=26.75µs, spill_count=0, spilled_bytes=0, mem_used=0]                                                                                                                                                                                                                                                                                                                                                                    |
|                        |   TskvExec: limit=None, predicate=ColumnDomains { column_to_domain: Some({}) }, projection=[station,visibility,temperature], metrics=[output_rows=13, elapsed_compute=13.225875ms, spill_count=0, spilled_bytes=0, mem_used=0, elapsed_point_to_record_batch=3.918163ms, elapsed_field_scan=3.992161ms, elapsed_series_scan=1.657416ms]                                                                                                                                                                                                                                 |
|                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| Plan with Full Metrics | ProjectionExec: expr=[station@0 as station, temperature@2 as temperature, visibility@1 as visibility], metrics=[start_timestamp{partition=0}=2022-10-25 03:00:14.865034 UTC, end_timestamp{partition=0}=2022-10-25 03:00:14.879596 UTC, elapsed_compute{partition=0}=26.75µs, spill_count{partition=0}=0, spilled_bytes{partition=0}=0, mem_used{partition=0}=0, output_rows{partition=0}=13]                                                                                                                                                                           |
|                        |   TskvExec: limit=None, predicate=ColumnDomains { column_to_domain: Some({}) }, projection=[station,visibility,temperature], metrics=[start_timestamp{partition=0}=2022-10-25 03:00:14.864225 UTC, end_timestamp{partition=0}=2022-10-25 03:00:14.879596 UTC, elapsed_compute{partition=0}=13.225875ms, spill_count{partition=0}=0, spilled_bytes{partition=0}=0, mem_used{partition=0}=0, output_rows{partition=0}=13, elapsed_point_to_record_batch{partition=0}=3.918163ms, elapsed_field_scan{partition=0}=3.992161ms, elapsed_series_scan{partition=0}=1.657416ms] |
|                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| Output Rows            | 13                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| Duration               | 13.307708ms                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
+------------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

DESCRIBE

语法

DESCRIBE {DATABASE db_name | TABLE tb_name};

描述数据库的参数，描述表的模式

示例

DESCRIBE TABLE air;

+-------------+-----------+-------+-------------+
| FIELDNAME   | TYPE      | ISTAG | COMPRESSION |
+-------------+-----------+-------+-------------+
| time        | TIMESTAMP | false | Default     |
| station     | STRING    | true  | Default     |
| visibility  | DOUBLE    | false | Default     |
| temperature | DOUBLE    | false | Default     |
| pressure    | DOUBLE    | false | Default     |
+-------------+-----------+-------+-------------+

DESCRIBE DATABASE public;

+----------+-------+----------------+---------+-----------+
| TTL      | SHARD | VNODE_DURATION | REPLICA | PRECISION |
+----------+-------+----------------+---------+-----------+
| 365 Days | 1     | 365 Days       | 1       | NS        |
+----------+-------+----------------+---------+-----------+

快速开始

示例数据​

下载数据​

导入数据​

语法​

SELECT 子句​

SELECT *​

ALL/DISTINCT​

别名​

为列表达式取别名​

为表取别名​

SELECT限制​

LIMIT 子句​

OFFSET 子句​

WITH 子句​

UNION 子句​

ORDER BY 子句​

IN​

SHOW​

EXPLAIN​

DESCRIBE​