Question

我在MySQL上的以下嵌套查询中尝试的任何内容都得到了相同的语法错误：

SELECT count(*) FROM TABLE_A AS A 
    WHERE A.COND = '2K' AND A.B_ID = : SELECT B.B_ID  
                                        FROM TABLE_B AS B
                                        WHERE B.NAME = 'XYZ';

请注意，TABLE_B上的NAME列条目是唯一的，并且对于查询逻辑不需要连接。

如何修复语法??

NaïveQ - 自本机SQL以来已经很久了。

TIA。

Answer 1

你需要在子查询周围做一些事情：

SELECT count(*)
FROM TABLE_A AS A 
WHERE A.COND = '2K' AND
      A.B_ID = (SELECT B.B_ID  
                FROM TABLE_B AS B
                WHERE B.NAME = 'XYZ');

如果它可以返回多个值，那么您需要in而不是=：

SELECT count(*)
FROM TABLE_A AS A 
WHERE A.COND = '2K' AND
      A.B_ID IN (SELECT B.B_ID  
                 FROM TABLE_B AS B
                 WHERE B.NAME = 'XYZ');

Answer 2

您可以避免使用显式子查询，而是使用显式连接：

SELECT COUNT(*) AS COUNT
  FROM TABLE_A AS A 
  JOIN TABLE_B AS B ON A.B_ID = B.B_ID
 WHERE A.COND = '2K'
   AND B.NAME = 'XYZ';

如果您想要子查询，那么Gordon Linoff的answer就可以了。

SQL内部查询语法

2 个答案: