子查询与比较操作符的使用

语法描述

子查询与比较操作符最常见的用法如下:

non_subquery_operand comparison_operator (subquery)

其中，comparison_operator 指以下操作符:

=  >  <  >=  <=  <>  !=  <=>

语法结构

> SELECT column_name(s) FROM table_name WHERE 'a' = (SELECT column1 FROM t1)

示例

> create table t1 (a int);
> create table t2 (a int, b int);
> create table t3 (a int);
> insert into t1 values (2);
> insert into t2 values (1,7),(2,7);
> insert into t3 values (6),(7),(3);
> select * from t3 where a = (select b from t2);
ERROR 1105 (HY000): scalar subquery returns more than 1 row
> select * from t3 where a = (select distinct b from t2);
+------+
| a    |
+------+
|    7 |
+------+
1 row in set (0.00 sec)

限制

MatrixOne 暂不支持选择多列进行子查询。