1.DECIMAL 类型不同于FLOAT和DECIMAL,其中DECIMAL 实际是以串存放的。DECIMAL 可能的最大取值范围与DOUBLE 一样,但是其有效的取值范围由M 和D 的值决定。如果改变M 而固定D,则其取值范围将随M 的变大而变大。2. binary保存二进制字符串,它保存的是字节而不是字符,没有字符集限制 binary(8)可以保存8个字符,每个字符占1个字节,共占8个字节 进行比较时是按字节进行比较,而不是按字符(char),按字节比较比字符简单快速 按字符比较不区分大小写,而binary区分大小写,结尾使用\0填充,而不是空格 mysql> select * from zcy where b='a\0\0\0\0\0\0\0'; +----+------+------+------+----------+ | id | name | addr | bn | b | +----+------+------+------+----------+ | 5 | t a | a | NULL | a | +----+------+------+------+----------+ mysql> select * from zcy where b='a \0\0\0\0\0\0'; +----+------+------+------+----------+ | id | name | addr | bn | b | +----+------+------+------+----------+ | 4 | a | a | ab | a | +----+------+------+------+----------+varbinary保存变长的字符串,后面不会补\0 mysql> select * from zcy where bn='ab'; +----+------+------+------+----------+ | id | name | addr | bn | b | +----+------+------+------+----------+ | 3 | a | a | ab | ab | +----+------+------+------+----------+ 1 row in set (0.01 sec)mysql> select * from zcy where bn='ab '; +----+------+------+------+----------+ | id | name | addr | bn | b | +----+------+------+------+----------+ | 2 | asdf | a | ab | ab | +----+------+------+------+----------+ 1 row in set (0.00 sec)mysql> select * from zcy where bn='ab '; +----+------+------+------+----------+ | id | name | addr | bn | b | +----+------+------+------+----------+ | 4 | a | a | ab | a | +----+------+------+------+----------+ 1 row in set (0.00 sec)
1.DECIMAL 类型不同于FLOAT和DECIMAL,其中DECIMAL 实际是以串存放的。DECIMAL 可能的最大取值范围与DOUBLE 一样,但是其有效的取值范围由M 和D 的值决定。如果改变M 而固定D,则其取值范围将随M 的变大而变大。2. binary保存二进制字符串,它保存的是字节而不是字符,没有字符集限制
binary(8)可以保存8个字符,每个字符占1个字节,共占8个字节
进行比较时是按字节进行比较,而不是按字符(char),按字节比较比字符简单快速
按字符比较不区分大小写,而binary区分大小写,结尾使用\0填充,而不是空格
mysql> select * from zcy where b='a\0\0\0\0\0\0\0';
+----+------+------+------+----------+
| id | name | addr | bn | b |
+----+------+------+------+----------+
| 5 | t a | a | NULL | a |
+----+------+------+------+----------+
mysql> select * from zcy where b='a \0\0\0\0\0\0';
+----+------+------+------+----------+
| id | name | addr | bn | b |
+----+------+------+------+----------+
| 4 | a | a | ab | a |
+----+------+------+------+----------+varbinary保存变长的字符串,后面不会补\0
mysql> select * from zcy where bn='ab';
+----+------+------+------+----------+
| id | name | addr | bn | b |
+----+------+------+------+----------+
| 3 | a | a | ab | ab |
+----+------+------+------+----------+
1 row in set (0.01 sec)mysql> select * from zcy where bn='ab ';
+----+------+------+------+----------+
| id | name | addr | bn | b |
+----+------+------+------+----------+
| 2 | asdf | a | ab | ab |
+----+------+------+------+----------+
1 row in set (0.00 sec)mysql> select * from zcy where bn='ab ';
+----+------+------+------+----------+
| id | name | addr | bn | b |
+----+------+------+------+----------+
| 4 | a | a | ab | a |
+----+------+------+------+----------+
1 row in set (0.00 sec)