PostgreSQL-为什么该语句会导致语法错误？

为什么此语句会在或附近导致语法错误？

请尝试以下操作-

SELECT
        (SELECT COUNT(*) FROM table1) AS count1 WHERE date='2019-06-12',
        (SELECT COUNT(*) FROM table2) AS count2 WHERE date='2019-06-12'

需要在子查询中添加where子句

SELECT
(SELECT COUNT(*) FROM table1 WHERE date='2019-06-12')  AS count1 ,
(SELECT COUNT(*) FROM table2 WHERE date='2019-06-12') AS count2 

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让我们重写语句，用一个简单的值替换括号中的SELECT：

SELECT
       (SELECT COUNT(*) FROM table1 WHERE date='2019-06-12') AS count1 ,
       (SELECT COUNT(*) FROM table2 WHERE date='2019-06-12') AS count2 

现在很容易看出，直到逗号为止，您都有一个有效的SQL查询，但是您添加了更多要选择的值，这是无效的

我假设您希望在子查询中包含where：

SELECT
        1 AS count1 WHERE date='2019-06-12',
        2 AS count2 WHERE date='2019-06-12'

SELECT
        (SELECT COUNT(*) FROM table1 WHERE date='2019-06-12') AS count1,
        (SELECT COUNT(*) FROM table2 WHERE date='2019-06-12') AS count2