mysql查询不同，性能不同

Question

下面的查询有什么区别？ id为主键

1, select id from tbl_xxx WHERE 2708 <= id <= 1562755185;
2, select id from tbl_xxx WHERE id> = 2708 and id <= 1562755185;
3, select id from tbl_xxx WHERE id between 2708 and 1562755185;

我发现性能不同，但不知道为什么？

explain select id from  tblData  WHERE  id >=   2708 and id <= 1562755185    ORDER BY id asc  LIMIT 652000, 1000\G; 
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: tblData
         type: range
possible_keys: PRIMARY
          key: PRIMARY
      key_len: 4
          ref: NULL
         rows: 30461948
        Extra: Using where; Using index

explain select id from  tblData  WHERE  2708 <= id <= 1562755185    ORDER BY id asc  LIMIT 652000, 1000\G;         *************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: tblData
         type: index
possible_keys: NULL
          key: PRIMARY
      key_len: 4
          ref: NULL
         rows: 653000
        Extra: Using where; Using index

Answer 1

查询2和3是等效的，因此它们应该执行相同的操作。查询1是完全不同的东西；查询 1 相当于:

select id from tbl_xxx WHERE (2708 <= id) <= 1562755185;

自 2708 <= id是一个 bool 表达式，MySQL 使用零和一作为 bool 值，你的查询总是比较 1 <= 1562755185或0 <= 1562755185因此退化为:

select id from tbl_xxx;

假设id当然永远不会是NULL。

因此，查询完全不同，没有理由期望它们执行相同的操作。

例如，我有一张 table ，看起来像这样:

mysql> select * from stars;
+----+-------+
| id | stars |
+----+-------+
|  1 |     1 |
|  2 |     2 |
|  3 |     3 |
|  4 |     2 |
|  5 |     1 |
|  6 |     1 |
|  7 |     1 |
|  8 |     2 |
|  9 |     1 |
+----+-------+

一个between这样做:

mysql> select * from stars where id between 3 and 5;
+----+-------+
| id | stars |
+----+-------+
|  3 |     3 |
|  4 |     2 |
|  5 |     1 |
+----+-------+

但是你的a <= id <= b这样做:

mysql> select * from stars where 3 <= id <= 5;
+----+-------+
| id | stars |
+----+-------+
|  1 |     1 |
|  2 |     2 |
|  3 |     3 |
|  4 |     2 |
|  5 |     1 |
|  6 |     1 |
|  7 |     1 |
|  8 |     2 |
|  9 |     1 |
+----+-------+