mysql where 子句的布尔值

Question

我想知道哪个更快？

SELECT * FROM `table` WHERE `is_deleted` = false;

或

SELECT * FROM `table` WHERE NOT `is_deleted`

谢谢

Answer 1

SELECT * 来自 table 而不是 is_deleted

此查询将为您提供更快、更合适的结果。

因为在 Mysql 中最好对布尔数据类型使用 Not 运算符。

Answer 2

架构

create table t123
(
    id int auto_increment primary key,
    x boolean not null,
    key(x)
);
truncate table t123;
insert t123(x) values (false),(true),(false),(true),(false),(true),(false),(true),(false),(true),(false),(true);
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;
insert t123(x) select (x) from t123;

select count(*) as rowCount from t123;
+----------+
| rowCount |
+----------+
|  3145728 |
+----------+

我们现在有 310 万行。

一个

explain SELECT * FROM t123 WHERE x=false;

+----+-------------+-------+------+---------------+------+---------+-------+---------+-------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref   | rows    | Extra       |
+----+-------------+-------+------+---------------+------+---------+-------+---------+-------------+
|  1 | SIMPLE      | t123  | ref  | x             | x    | 1       | const | 1570707 | Using index |
+----+-------------+-------+------+---------------+------+---------+-------+---------+-------------+

B

explain SELECT * FROM t123 WHERE NOT `x`;

+----+-------------+-------+-------+---------------+------+---------+------+---------+--------------------------+
| id | select_type | table | type  | possible_keys | key  | key_len | ref  | rows    | Extra                    |
+----+-------------+-------+-------+---------------+------+---------+------+---------+--------------------------+
|  1 | SIMPLE      | t123  | index | NULL          | x    | 1       | NULL | 3141414 | Using where; Using index |
+----+-------------+-------+-------+---------------+------+---------+------+---------+--------------------------+

所以 A 更快，因为它能够使用本机数据类型（如在具有它的索引中所见），并且由于 table 的方式 B 处理数据转换（并且确实导致 table 扫描）

它的证明在 explain 输出中，需要 rows 的数量来确定答案，并且缺少索引的使用（ref列）甚至在两个查询的列上。

Mysql Explain Syntax 的手册页。

mysql where 子句的布尔值

mysql boolean on where clause

mysql

boolean

where-clause

架构

一个

B