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SELECT

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SELECT 语句用于从表中选取数据。SELECT语句是查询语法的核心,所有高级查询语法都是围绕SELECT语句展开的。本节将简单支持的SELECT语句语法,高级用法请参考其他的小节。

语法格式

SELECT:
  SELECT [ DISTINCT ]
  	{ * | projectItem [, projectItem ]* }
  FROM tableExpression
  	[ WHERE booleanExpression ]
  	[ GROUP BY { groupItem [, groupItem ]* } ]
    [ ORDER BY { orderByItem [, OrderByItem ]* }]
  	[ HAVING booleanExpression ]
    [ LIMIT number]
    [ OFFSET number]
  
projectItem:
  expression [ [ AS ] columnAlias ]
  | tableAlias . *

示例

SELECT * FROM table;

SELECT f1, f2 AS ff FROM table;

SELECT DISTINCT f FROM table;

SELECT * FROM (
      SELECT f1, count(*) AS num
      FROM t1
      GROUP BY f1
  ) tt
  WHERE tt.num > 100;