INT类型
类型
image.png
tinyintsmallinitmediumintintbigint
属性
-
signed / unsigned- 有符号 / 无符号
mysql> create table a ( a int(10) , b int(10) unsigned );
Query OK, 0 rows affected (0.02 sec)
mysql> show create table a\G;
*************************** 1. row ***************************
Table: a
Create Table: CREATE TABLE `a` (
`a` int(10) DEFAULT NULL,
`b` int(10) unsigned DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
ERROR:
No query specified
mysql>
-
zerofill- 显示属性，值不做任何修改
mysql> create table b ( id int(3) );
Query OK, 0 rows affected (0.03 sec)
mysql> insert into b select 5;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from b;
+------+
| id |
+------+
| 5 |
+------+
1 row in set (0.00 sec)
mysql> insert into b values (12345);
Query OK, 1 row affected (0.00 sec)
mysql> select * from b;
+-------+
| id |
+-------+
| 5 |
| 12345 |
+-------+
2 rows in set (0.00 sec)
mysql> create table c ( id int(3) zerofill );
Query OK, 0 rows affected (0.02 sec)
mysql> insert into c select 5;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from c;
+------+
| id |
+------+
| 005 |
+------+
1 row in set (0.01 sec)
mysql> insert into c select 12345;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from c;
+-------+
| id |
+-------+
| 005 |
| 12345 |
+-------+
2 rows in set (0.00 sec)
mysql> show create table b\G;
*************************** 1. row ***************************
Table: b
Create Table: CREATE TABLE `b` (
`id` int(3) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
ERROR:
No query specified
mysql> show create table c\G;
*************************** 1. row ***************************
Table: c
Create Table: CREATE TABLE `c` (
`id` int(3) unsigned zerofill DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
ERROR:
No query specified
mysql>
int(5)类型的宽度为 5 ，默认不补全，当加上
zerofill，当宽度不足设定的宽度时，自动在前面补0，同时类型是无符号的unsigned
- auto_increment
- 自增长，每张表只能有一个，必须是索引的一部分
mysql> create table d ( id bigint auto_increment );
ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key
mysql>
# 必须加上索引
mysql> create table d ( id bigint auto_increment primary key );
Query OK, 0 rows affected (0.03 sec)
mysql> show create table d\G;
*************************** 1. row ***************************
Table: d
Create Table: CREATE TABLE `d` (
`id` bigint(20) NOT NULL AUTO_INCREMENT,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
ERROR:
No query specified
mysql>
• 推荐不要使用UNSIGNED
• 范围本质上没有大的改变
• UNSIGNED可能会有溢出现象发生
• 自增INT类型主键建议使用BIGINT
数字类型
image.png
- 单精度类型：float
- 双精度类型：double
- 高精度类型：decimal
M*G/G 不一定等于M
FLOAT(M,D)/DOUBLE(M,D)/DECIMAL(M,D) 表示显示M位整数，其中D位位于小数点后面
财务、财务系统必须使用
DECIMAL类型
字符串类型
image.png
char 和 varchar 的区别
char(N)，varchar(N) 的 N 都表示 字符，
char是定长字符，根据定义的字符串长度分配足够的空间，适合存储很短的字符串或固定的字符串，比如手机号，固定11位。varchar用于存储可变长字符串，它比 char 更节省空间。
如果 长度超过设定的长度，char、varchar都会被截断。
- 在BLOB和TEXT列上创建索引时，必须制定索引前缀的长度
- VARCHAR和VARBINARY前缀长度是可选的。
- BLOB和TEXT列不能有默认值
- BLOB和TEXT列排序时只使用该列的前max_sort_length个字节
mysql> create table a ( `a` text, key `a`(`a`) );
ERROR 1170 (42000): BLOB/TEXT column 'a' used in key specification without a key length
# 必须制定索引前缀的长度
mysql>
mysql> create table a ( `a` text, key `a`(`a` (255)) );
Query OK, 0 rows affected (0.04 sec)
mysql> show create table a\G;
*************************** 1. row ***************************
Table: a
Create Table: CREATE TABLE `a` (
`a` text,
KEY `a` (`a`(255))
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
ERROR:
No query specified
mysql>
mysql> select @@global.max_sort_length;
+--------------------------+
| @@global.max_sort_length |
+--------------------------+
| 1024 |
+--------------------------+
1 row in set (0.00 sec)
mysql>
字符集
- character set
- a set of symbols and encodings.
- 常见的字符集：utf8、utfmb4、gbk、gb18030
查看所有的字符集
mysql> show character set;
+----------+---------------------------------+---------------------+--------+
| Charset | Description | Default collation | Maxlen |
+----------+---------------------------------+---------------------+--------+
| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |
| dec8 | DEC West European | dec8_swedish_ci | 1 |
| cp850 | DOS West European | cp850_general_ci | 1 |
| hp8 | HP West European | hp8_english_ci | 1 |
| koi8r | KOI8-R Relcom Russian | koi8r_general_ci | 1 |
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
| latin2 | ISO 8859-2 Central European | latin2_general_ci | 1 |
| swe7 | 7bit Swedish | swe7_swedish_ci | 1 |
| ascii | US ASCII | ascii_general_ci | 1 |
| ujis | EUC-JP Japanese | ujis_japanese_ci | 3 |
| sjis | Shift-JIS Japanese | sjis_japanese_ci | 2 |
| hebrew | ISO 8859-8 Hebrew | hebrew_general_ci | 1 |
| tis620 | TIS620 Thai | tis620_thai_ci | 1 |
| euckr | EUC-KR Korean | euckr_korean_ci | 2 |
| koi8u | KOI8-U Ukrainian | koi8u_general_ci | 1 |
| gb2312 | GB2312 Simplified Chinese | gb2312_chinese_ci | 2 |
| greek | ISO 8859-7 Greek | greek_general_ci | 1 |
| cp1250 | Windows Central European | cp1250_general_ci | 1 |
| gbk | GBK Simplified Chinese | gbk_chinese_ci | 2 |
| latin5 | ISO 8859-9 Turkish | latin5_turkish_ci | 1 |
| armscii8 | ARMSCII-8 Armenian | armscii8_general_ci | 1 |
| utf8 | UTF-8 Unicode | utf8_general_ci | 3 |
| ucs2 | UCS-2 Unicode | ucs2_general_ci | 2 |
| cp866 | DOS Russian | cp866_general_ci | 1 |
| keybcs2 | DOS Kamenicky Czech-Slovak | keybcs2_general_ci | 1 |
| macce | Mac Central European | macce_general_ci | 1 |
| macroman | Mac West European | macroman_general_ci | 1 |
| cp852 | DOS Central European | cp852_general_ci | 1 |
| latin7 | ISO 8859-13 Baltic | latin7_general_ci | 1 |
| utf8mb4 | UTF-8 Unicode | utf8mb4_general_ci | 4 |
| cp1251 | Windows Cyrillic | cp1251_general_ci | 1 |
| utf16 | UTF-16 Unicode | utf16_general_ci | 4 |
| utf16le | UTF-16LE Unicode | utf16le_general_ci | 4 |
| cp1256 | Windows Arabic | cp1256_general_ci | 1 |
| cp1257 | Windows Baltic | cp1257_general_ci | 1 |
| utf32 | UTF-32 Unicode | utf32_general_ci | 4 |
| binary | Binary pseudo charset | binary | 1 |
| geostd8 | GEOSTD8 Georgian | geostd8_general_ci | 1 |
| cp932 | SJIS for Windows Japanese | cp932_japanese_ci | 2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci | 3 |
| gb18030 | China National Standard GB18030 | gb18030_chinese_ci | 4 |
+----------+---------------------------------+---------------------+--------+
41 rows in set (0.00 sec)
字符集的设置
- 配置参数character_set_server
- CREATE DATABASE
- CREATE TABLE
CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] db_name
[create_specification] ...
create_specification:
[DEFAULT] CHARACTER SET [=] charset_name
| [DEFAULT] COLLATE [=] collation_name
mysql> create table g ( `a` char(10) ) charset=utf8mb4;
Query OK, 0 rows affected (0.03 sec)
mysql> show create table g\G;
*************************** 1. row ***************************
Table: g
Create Table: CREATE TABLE `g` (
`a` char(10) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
ERROR:
No query specified
mysql>
mysql> create table h ( `a` varchar(60) charset gbk, `b` char(11) charset utf8, `c` varchar(100) charset utf8mb4 );
Query OK, 0 rows affected (0.02 sec)
mysql> show create table h\G;
*************************** 1. row ***************************
Table: h
Create Table: CREATE TABLE `h` (
`a` varchar(60) CHARACTER SET gbk DEFAULT NULL,
`b` char(11) CHARACTER SET utf8 DEFAULT NULL,
`c` varchar(100) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
ERROR:
No query specified
mysql>
排序规则
- collation
- set of rules for comparing characters in a character set
查看所有的排序规则
mysql> show collation;
+--------------------------+----------+-----+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+--------------------------+----------+-----+---------+----------+---------+
| big5_chinese_ci | big5 | 1 | Yes | Yes | 1 |
| big5_bin | big5 | 84 | | Yes | 1 |
| dec8_swedish_ci | dec8 | 3 | Yes | Yes | 1 |
| dec8_bin | dec8 | 69 | | Yes | 1 |
| cp850_general_ci | cp850 | 4 | Yes | Yes | 1 |
| cp850_bin | cp850 | 80 | | Yes | 1 |
| hp8_english_ci | hp8 | 6 | Yes | Yes | 1 |
| hp8_bin | hp8 | 72 | | Yes | 1 |
| koi8r_general_ci | koi8r | 7 | Yes | Yes | 1 |
| koi8r_bin | koi8r | 74 | | Yes | 1 |
| latin1_german1_ci | latin1 | 5 | | Yes | 1 |
| latin1_swedish_ci | latin1 | 8 | Yes | Yes | 1 |
| latin1_danish_ci | latin1 | 15 | | Yes | 1 |
| latin1_german2_ci | latin1 | 31 | | Yes | 2 |
| latin1_bin | latin1 | 47 | | Yes | 1 |
| latin1_general_ci | latin1 | 48 | | Yes | 1 |
| latin1_general_cs | latin1 | 49 | | Yes | 1 |
| latin1_spanish_ci | latin1 | 94 | | Yes | 1 |
| latin2_czech_cs | latin2 | 2 | | Yes | 4 |
| latin2_general_ci | latin2 | 9 | Yes | Yes | 1 |
| latin2_hungarian_ci | latin2 | 21 | | Yes | 1 |
| latin2_croatian_ci | latin2 | 27 | | Yes | 1 |
| latin2_bin | latin2 | 77 | | Yes | 1 |
| swe7_swedish_ci | swe7 | 10 | Yes | Yes | 1 |
| swe7_bin | swe7 | 82 | | Yes | 1 |
| ascii_general_ci | ascii | 11 | Yes | Yes | 1 |
| ascii_bin | ascii | 65 | | Yes | 1 |
| ujis_japanese_ci | ujis | 12 | Yes | Yes | 1 |
| ujis_bin | ujis | 91 | | Yes | 1 |
| sjis_japanese_ci | sjis | 13 | Yes | Yes | 1 |
| sjis_bin | sjis | 88 | | Yes | 1 |
| hebrew_general_ci | hebrew | 16 | Yes | Yes | 1 |
| hebrew_bin | hebrew | 71 | | Yes | 1 |
| tis620_thai_ci | tis620 | 18 | Yes | Yes | 4 |
| tis620_bin | tis620 | 89 | | Yes | 1 |
| euckr_korean_ci | euckr | 19 | Yes | Yes | 1 |
| euckr_bin | euckr | 85 | | Yes | 1 |
| koi8u_general_ci | koi8u | 22 | Yes | Yes | 1 |
| koi8u_bin | koi8u | 75 | | Yes | 1 |
| gb2312_chinese_ci | gb2312 | 24 | Yes | Yes | 1 |
| gb2312_bin | gb2312 | 86 | | Yes | 1 |
| greek_general_ci | greek | 25 | Yes | Yes | 1 |
| greek_bin | greek | 70 | | Yes | 1 |
| cp1250_general_ci | cp1250 | 26 | Yes | Yes | 1 |
| cp1250_czech_cs | cp1250 | 34 | | Yes | 2 |
| cp1250_croatian_ci | cp1250 | 44 | | Yes | 1 |
| cp1250_bin | cp1250 | 66 | | Yes | 1 |
| cp1250_polish_ci | cp1250 | 99 | | Yes | 1 |
| gbk_chinese_ci | gbk | 28 | Yes | Yes | 1 |
| gbk_bin | gbk | 87 | | Yes | 1 |
| latin5_turkish_ci | latin5 | 30 | Yes | Yes | 1 |
| latin5_bin | latin5 | 78 | | Yes | 1 |
| armscii8_general_ci | armscii8 | 32 | Yes | Yes | 1 |
| armscii8_bin | armscii8 | 64 | | Yes | 1 |
| utf8_general_ci | utf8 | 33 | Yes | Yes | 1 |
| utf8_bin | utf8 | 83 | | Yes | 1 |
| utf8_unicode_ci | utf8 | 192 | | Yes | 8 |
| utf8_icelandic_ci | utf8 | 193 | | Yes | 8 |
| utf8_latvian_ci | utf8 | 194 | | Yes | 8 |
| utf8_romanian_ci | utf8 | 195 | | Yes | 8 |
| utf8_slovenian_ci | utf8 | 196 | | Yes | 8 |
| utf8_polish_ci | utf8 | 197 | | Yes | 8 |
| utf8_estonian_ci | utf8 | 198 | | Yes | 8 |
| utf8_spanish_ci | utf8 | 199 | | Yes | 8 |
| utf8_swedish_ci | utf8 | 200 | | Yes | 8 |
| utf8_turkish_ci | utf8 | 201 | | Yes | 8 |
| utf8_czech_ci | utf8 | 202 | | Yes | 8 |
| utf8_danish_ci | utf8 | 203 | | Yes | 8 |
| utf8_lithuanian_ci | utf8 | 204 | | Yes | 8 |
| utf8_slovak_ci | utf8 | 205 | | Yes | 8 |
| utf8_spanish2_ci | utf8 | 206 | | Yes | 8 |
| utf8_roman_ci | utf8 | 207 | | Yes | 8 |
| utf8_persian_ci | utf8 | 208 | | Yes | 8 |
| utf8_esperanto_ci | utf8 | 209 | | Yes | 8 |
| utf8_hungarian_ci | utf8 | 210 | | Yes | 8 |
| utf8_sinhala_ci | utf8 | 211 | | Yes | 8 |
| utf8_german2_ci | utf8 | 212 | | Yes | 8 |
| utf8_croatian_ci | utf8 | 213 | | Yes | 8 |
| utf8_unicode_520_ci | utf8 | 214 | | Yes | 8 |
| utf8_vietnamese_ci | utf8 | 215 | | Yes | 8 |
| utf8_general_mysql500_ci | utf8 | 223 | | Yes | 1 |
| ucs2_general_ci | ucs2 | 35 | Yes | Yes | 1 |
| ucs2_bin | ucs2 | 90 | | Yes | 1 |
| ucs2_unicode_ci | ucs2 | 128 | | Yes | 8 |
| ucs2_icelandic_ci | ucs2 | 129 | | Yes | 8 |
| ucs2_latvian_ci | ucs2 | 130 | | Yes | 8 |
| ucs2_romanian_ci | ucs2 | 131 | | Yes | 8 |
| ucs2_slovenian_ci | ucs2 | 132 | | Yes | 8 |
| ucs2_polish_ci | ucs2 | 133 | | Yes | 8 |
| ucs2_estonian_ci | ucs2 | 134 | | Yes | 8 |
| ucs2_spanish_ci | ucs2 | 135 | | Yes | 8 |
| ucs2_swedish_ci | ucs2 | 136 | | Yes | 8 |
| ucs2_turkish_ci | ucs2 | 137 | | Yes | 8 |
| ucs2_czech_ci | ucs2 | 138 | | Yes | 8 |
| ucs2_danish_ci | ucs2 | 139 | | Yes | 8 |
| ucs2_lithuanian_ci | ucs2 | 140 | | Yes | 8 |
| ucs2_slovak_ci | ucs2 | 141 | | Yes | 8 |
| ucs2_spanish2_ci | ucs2 | 142 | | Yes | 8 |
| ucs2_roman_ci | ucs2 | 143 | | Yes | 8 |
| ucs2_persian_ci | ucs2 | 144 | | Yes | 8 |
| ucs2_esperanto_ci | ucs2 | 145 | | Yes | 8 |
| ucs2_hungarian_ci | ucs2 | 146 | | Yes | 8 |
| ucs2_sinhala_ci | ucs2 | 147 | | Yes | 8 |
| ucs2_german2_ci | ucs2 | 148 | | Yes | 8 |
| ucs2_croatian_ci | ucs2 | 149 | | Yes | 8 |
| ucs2_unicode_520_ci | ucs2 | 150 | | Yes | 8 |
| ucs2_vietnamese_ci | ucs2 | 151 | | Yes | 8 |
| ucs2_general_mysql500_ci | ucs2 | 159 | | Yes | 1 |
| cp866_general_ci | cp866 | 36 | Yes | Yes | 1 |
| cp866_bin | cp866 | 68 | | Yes | 1 |
| keybcs2_general_ci | keybcs2 | 37 | Yes | Yes | 1 |
| keybcs2_bin | keybcs2 | 73 | | Yes | 1 |
| macce_general_ci | macce | 38 | Yes | Yes | 1 |
| macce_bin | macce | 43 | | Yes | 1 |
| macroman_general_ci | macroman | 39 | Yes | Yes | 1 |
| macroman_bin | macroman | 53 | | Yes | 1 |
| cp852_general_ci | cp852 | 40 | Yes | Yes | 1 |
| cp852_bin | cp852 | 81 | | Yes | 1 |
| latin7_estonian_cs | latin7 | 20 | | Yes | 1 |
| latin7_general_ci | latin7 | 41 | Yes | Yes | 1 |
| latin7_general_cs | latin7 | 42 | | Yes | 1 |
| latin7_bin | latin7 | 79 | | Yes | 1 |
| utf8mb4_general_ci | utf8mb4 | 45 | Yes | Yes | 1 |
| utf8mb4_bin | utf8mb4 | 46 | | Yes | 1 |
| utf8mb4_unicode_ci | utf8mb4 | 224 | | Yes | 8 |
| utf8mb4_icelandic_ci | utf8mb4 | 225 | | Yes | 8 |
| utf8mb4_latvian_ci | utf8mb4 | 226 | | Yes | 8 |
| utf8mb4_romanian_ci | utf8mb4 | 227 | | Yes | 8 |
| utf8mb4_slovenian_ci | utf8mb4 | 228 | | Yes | 8 |
| utf8mb4_polish_ci | utf8mb4 | 229 | | Yes | 8 |
| utf8mb4_estonian_ci | utf8mb4 | 230 | | Yes | 8 |
| utf8mb4_spanish_ci | utf8mb4 | 231 | | Yes | 8 |
| utf8mb4_swedish_ci | utf8mb4 | 232 | | Yes | 8 |
| utf8mb4_turkish_ci | utf8mb4 | 233 | | Yes | 8 |
| utf8mb4_czech_ci | utf8mb4 | 234 | | Yes | 8 |
| utf8mb4_danish_ci | utf8mb4 | 235 | | Yes | 8 |
| utf8mb4_lithuanian_ci | utf8mb4 | 236 | | Yes | 8 |
| utf8mb4_slovak_ci | utf8mb4 | 237 | | Yes | 8 |
| utf8mb4_spanish2_ci | utf8mb4 | 238 | | Yes | 8 |
| utf8mb4_roman_ci | utf8mb4 | 239 | | Yes | 8 |
| utf8mb4_persian_ci | utf8mb4 | 240 | | Yes | 8 |
| utf8mb4_esperanto_ci | utf8mb4 | 241 | | Yes | 8 |
| utf8mb4_hungarian_ci | utf8mb4 | 242 | | Yes | 8 |
| utf8mb4_sinhala_ci | utf8mb4 | 243 | | Yes | 8 |
| utf8mb4_german2_ci | utf8mb4 | 244 | | Yes | 8 |
| utf8mb4_croatian_ci | utf8mb4 | 245 | | Yes | 8 |
| utf8mb4_unicode_520_ci | utf8mb4 | 246 | | Yes | 8 |
| utf8mb4_vietnamese_ci | utf8mb4 | 247 | | Yes | 8 |
| cp1251_bulgarian_ci | cp1251 | 14 | | Yes | 1 |
| cp1251_ukrainian_ci | cp1251 | 23 | | Yes | 1 |
| cp1251_bin | cp1251 | 50 | | Yes | 1 |
| cp1251_general_ci | cp1251 | 51 | Yes | Yes | 1 |
| cp1251_general_cs | cp1251 | 52 | | Yes | 1 |
| utf16_general_ci | utf16 | 54 | Yes | Yes | 1 |
| utf16_bin | utf16 | 55 | | Yes | 1 |
| utf16_unicode_ci | utf16 | 101 | | Yes | 8 |
| utf16_icelandic_ci | utf16 | 102 | | Yes | 8 |
| utf16_latvian_ci | utf16 | 103 | | Yes | 8 |
| utf16_romanian_ci | utf16 | 104 | | Yes | 8 |
| utf16_slovenian_ci | utf16 | 105 | | Yes | 8 |
| utf16_polish_ci | utf16 | 106 | | Yes | 8 |
| utf16_estonian_ci | utf16 | 107 | | Yes | 8 |
| utf16_spanish_ci | utf16 | 108 | | Yes | 8 |
| utf16_swedish_ci | utf16 | 109 | | Yes | 8 |
| utf16_turkish_ci | utf16 | 110 | | Yes | 8 |
| utf16_czech_ci | utf16 | 111 | | Yes | 8 |
| utf16_danish_ci | utf16 | 112 | | Yes | 8 |
| utf16_lithuanian_ci | utf16 | 113 | | Yes | 8 |
| utf16_slovak_ci | utf16 | 114 | | Yes | 8 |
| utf16_spanish2_ci | utf16 | 115 | | Yes | 8 |
| utf16_roman_ci | utf16 | 116 | | Yes | 8 |
| utf16_persian_ci | utf16 | 117 | | Yes | 8 |
| utf16_esperanto_ci | utf16 | 118 | | Yes | 8 |
| utf16_hungarian_ci | utf16 | 119 | | Yes | 8 |
| utf16_sinhala_ci | utf16 | 120 | | Yes | 8 |
| utf16_german2_ci | utf16 | 121 | | Yes | 8 |
| utf16_croatian_ci | utf16 | 122 | | Yes | 8 |
| utf16_unicode_520_ci | utf16 | 123 | | Yes | 8 |
| utf16_vietnamese_ci | utf16 | 124 | | Yes | 8 |
| utf16le_general_ci | utf16le | 56 | Yes | Yes | 1 |
| utf16le_bin | utf16le | 62 | | Yes | 1 |
| cp1256_general_ci | cp1256 | 57 | Yes | Yes | 1 |
| cp1256_bin | cp1256 | 67 | | Yes | 1 |
| cp1257_lithuanian_ci | cp1257 | 29 | | Yes | 1 |
| cp1257_bin | cp1257 | 58 | | Yes | 1 |
| cp1257_general_ci | cp1257 | 59 | Yes | Yes | 1 |
| utf32_general_ci | utf32 | 60 | Yes | Yes | 1 |
| utf32_bin | utf32 | 61 | | Yes | 1 |
| utf32_unicode_ci | utf32 | 160 | | Yes | 8 |
| utf32_icelandic_ci | utf32 | 161 | | Yes | 8 |
| utf32_latvian_ci | utf32 | 162 | | Yes | 8 |
| utf32_romanian_ci | utf32 | 163 | | Yes | 8 |
| utf32_slovenian_ci | utf32 | 164 | | Yes | 8 |
| utf32_polish_ci | utf32 | 165 | | Yes | 8 |
| utf32_estonian_ci | utf32 | 166 | | Yes | 8 |
| utf32_spanish_ci | utf32 | 167 | | Yes | 8 |
| utf32_swedish_ci | utf32 | 168 | | Yes | 8 |
| utf32_turkish_ci | utf32 | 169 | | Yes | 8 |
| utf32_czech_ci | utf32 | 170 | | Yes | 8 |
| utf32_danish_ci | utf32 | 171 | | Yes | 8 |
| utf32_lithuanian_ci | utf32 | 172 | | Yes | 8 |
| utf32_slovak_ci | utf32 | 173 | | Yes | 8 |
| utf32_spanish2_ci | utf32 | 174 | | Yes | 8 |
| utf32_roman_ci | utf32 | 175 | | Yes | 8 |
| utf32_persian_ci | utf32 | 176 | | Yes | 8 |
| utf32_esperanto_ci | utf32 | 177 | | Yes | 8 |
| utf32_hungarian_ci | utf32 | 178 | | Yes | 8 |
| utf32_sinhala_ci | utf32 | 179 | | Yes | 8 |
| utf32_german2_ci | utf32 | 180 | | Yes | 8 |
| utf32_croatian_ci | utf32 | 181 | | Yes | 8 |
| utf32_unicode_520_ci | utf32 | 182 | | Yes | 8 |
| utf32_vietnamese_ci | utf32 | 183 | | Yes | 8 |
| binary | binary | 63 | Yes | Yes | 1 |
| geostd8_general_ci | geostd8 | 92 | Yes | Yes | 1 |
| geostd8_bin | geostd8 | 93 | | Yes | 1 |
| cp932_japanese_ci | cp932 | 95 | Yes | Yes | 1 |
| cp932_bin | cp932 | 96 | | Yes | 1 |
| eucjpms_japanese_ci | eucjpms | 97 | Yes | Yes | 1 |
| eucjpms_bin | eucjpms | 98 | | Yes | 1 |
| gb18030_chinese_ci | gb18030 | 248 | Yes | Yes | 2 |
| gb18030_bin | gb18030 | 249 | | Yes | 1 |
| gb18030_unicode_520_ci | gb18030 | 250 | | Yes | 8 |
+--------------------------+----------+-----+---------+----------+---------+
222 rows in set (0.00 sec)
mysql>
排序规则中..._ci表示不区分大小写，比如：默认的排序规则utf8mb4_general_ci
mysql> show collation like 'utf8mb4%';
+------------------------+---------+-----+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+------------------------+---------+-----+---------+----------+---------+
| utf8mb4_general_ci | utf8mb4 | 45 | Yes | Yes | 1 |
| utf8mb4_bin | utf8mb4 | 46 | | Yes | 1 |
| utf8mb4_unicode_ci | utf8mb4 | 224 | | Yes | 8 |
| utf8mb4_icelandic_ci | utf8mb4 | 225 | | Yes | 8 |
| utf8mb4_latvian_ci | utf8mb4 | 226 | | Yes | 8 |
| utf8mb4_romanian_ci | utf8mb4 | 227 | | Yes | 8 |
| utf8mb4_slovenian_ci | utf8mb4 | 228 | | Yes | 8 |
| utf8mb4_polish_ci | utf8mb4 | 229 | | Yes | 8 |
| utf8mb4_estonian_ci | utf8mb4 | 230 | | Yes | 8 |
| utf8mb4_spanish_ci | utf8mb4 | 231 | | Yes | 8 |
| utf8mb4_swedish_ci | utf8mb4 | 232 | | Yes | 8 |
| utf8mb4_turkish_ci | utf8mb4 | 233 | | Yes | 8 |
| utf8mb4_czech_ci | utf8mb4 | 234 | | Yes | 8 |
| utf8mb4_danish_ci | utf8mb4 | 235 | | Yes | 8 |
| utf8mb4_lithuanian_ci | utf8mb4 | 236 | | Yes | 8 |
| utf8mb4_slovak_ci | utf8mb4 | 237 | | Yes | 8 |
| utf8mb4_spanish2_ci | utf8mb4 | 238 | | Yes | 8 |
| utf8mb4_roman_ci | utf8mb4 | 239 | | Yes | 8 |
| utf8mb4_persian_ci | utf8mb4 | 240 | | Yes | 8 |
| utf8mb4_esperanto_ci | utf8mb4 | 241 | | Yes | 8 |
| utf8mb4_hungarian_ci | utf8mb4 | 242 | | Yes | 8 |
| utf8mb4_sinhala_ci | utf8mb4 | 243 | | Yes | 8 |
| utf8mb4_german2_ci | utf8mb4 | 244 | | Yes | 8 |
| utf8mb4_croatian_ci | utf8mb4 | 245 | | Yes | 8 |
| utf8mb4_unicode_520_ci | utf8mb4 | 246 | | Yes | 8 |
| utf8mb4_vietnamese_ci | utf8mb4 | 247 | | Yes | 8 |
+------------------------+---------+-----+---------+----------+---------+
26 rows in set (0.00 sec)
mysql>
mysql> select 'a' = 'a';
+-----------+
| 'a' = 'a' |
+-----------+
| 1 |
+-----------+
1 row in set (0.00 sec)
mysql> select 'a' = 'A';
+-----------+
| 'a' = 'A' |
+-----------+
| 1 |
+-----------+
1 row in set (0.00 sec)
mysql>
mysql> select 'a' = 'a ';
+------------+
| 'a' = 'a ' |
+------------+
| 1 |
+------------+
1 row in set (0.00 sec)
mysql> select 'a' = 'A ';
+------------+
| 'a' = 'A ' |
+------------+
| 1 |
+------------+
1 row in set (0.00 sec)
mysql>
设置排序规则为utf8mb4_bin后，区分大小写
mysql> set names utf8mb4 collate utf8mb4_bin;
Query OK, 0 rows affected (0.00 sec)
mysql> select 'a' = 'A';
+-----------+
| 'a' = 'A' |
+-----------+
| 0 |
+-----------+
1 row in set (0.00 sec)
mysql>
集合类型
- ENUM
- ENUM类型最多允许65536个值
- SET
- SET类型最多允许64个值
通过sql_mode参数可以用于约束检查
mysql> create table f ( username varchar(50), sex enum ('0', '1') );
Query OK, 0 rows affected (0.06 sec)
mysql>
mysql> set sql_mode = 'strict_trans_tables';
Query OK, 0 rows affected, 2 warnings (0.00 sec)
mysql> insert into f select 'Jim', '1';
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> insert into f select 'Alisa', '0';
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> insert into f select 'Tom', '2';
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from f;
+----------+------+
| username | sex |
+----------+------+
| Jim | 1 |
| Alisa | 0 |
| Tom | 1 |
+----------+------+
3 rows in set (0.00 sec)
日期类型
image.png
datetime 和 timestamp 的区别
- 表示的范围不同
- timestamp有时区、datetime没有时区
mysql> show variables like 'time_zone';
+---------------+--------+
| Variable_name | Value |
+---------------+--------+
| time_zone | SYSTEM |
+---------------+--------+
1 row in set (0.00 sec)
mysql> create table i ( a datetime, b timestamp );
Query OK, 0 rows affected (0.03 sec)
mysql> show create table i\G
*************************** 1. row ***************************
Table: i
Create Table: CREATE TABLE `i` (
`a` datetime DEFAULT NULL,
`b` timestamp NULL DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
mysql> insert into i select now(), now();
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> select * from i;
+---------------------+---------------------+
| a | b |
+---------------------+---------------------+
| 2019-05-29 16:40:38 | 2019-05-29 16:40:38 |
+---------------------+---------------------+
1 row in set (0.00 sec)
mysql> set time_zone = '+00:00';
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> show variables like 'time_zone';
+---------------+--------+
| Variable_name | Value |
+---------------+--------+
| time_zone | +00:00 |
+---------------+--------+
1 row in set (0.00 sec)
mysql> select * from i;
+---------------------+---------------------+
| a | b |
+---------------------+---------------------+
| 2019-05-29 16:40:38 | 2019-05-29 08:40:38 |
+---------------------+---------------------+
1 row in set (0.00 sec)
日期函数
image.png
mysql从5.6.4开始支持微秒时间，type_name(fsp)，fsp最大为6
mysql> select now();
+---------------------+
| now() |
+---------------------+
| 2019-05-29 08:56:59 |
+---------------------+
1 row in set (0.00 sec)
mysql> select now(6);
+----------------------------+
| now(6) |
+----------------------------+
| 2019-05-29 08:57:09.291140 |
+----------------------------+
1 row in set (0.00 sec)
mysql> select now(7);
ERROR 1426 (42000): Too-big precision 7 specified for 'now'. Maximum is 6.
mysql>
now与sysdate区别
mysql> select now(), sysdate(), sleep(5), now(), sysdate();
+---------------------+---------------------+----------+---------------------+---------------------+
| now() | sysdate() | sleep(5) | now() | sysdate() |
+---------------------+---------------------+----------+---------------------+---------------------+
| 2019-05-29 09:05:03 | 2019-05-29 09:05:03 | 0 | 2019-05-29 09:05:03 | 2019-05-29 09:05:08 |
+---------------------+---------------------+----------+---------------------+---------------------+
1 row in set (5.00 sec)
mysql>
mysql> select now(6), sysdate(6);
+----------------------------+----------------------------+
| now(6) | sysdate(6) |
+----------------------------+----------------------------+
| 2019-05-29 09:06:36.635988 | 2019-05-29 09:06:36.636069 |
+----------------------------+----------------------------+
1 row in set (0.00 sec)
mysql>
json类型
- 5.7版本开始支持
- 原生JSON类型替换BLOB类型
- JSON数据有效性检查:BLOB类型无法在数据库层做这样的约束性检查
- 查询性能的提升:查询不需要遍历所有字符串才能找到数据
- 支持部分属性索引:通过虚拟列的功能可以对JSON中的部分数据进行索引
mysql> create table user ( id int auto_increment primary key, data json );
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id: 9
Current database: test
Query OK, 0 rows affected (0.02 sec)
mysql> show create table user\G
*************************** 1. row ***************************
Table: user
Create Table: CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`data` json DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
mysql> insert into user select null, '{"name": "Chase", "age": 25, "email": "czhd2552@163.com"}';
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> insert into user select null, '{"name": "Alisa", "address": "GuangZhou"}';
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql>
mysql> insert into user select null, '{}';
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> insert into user select null, null;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
# 当data的值不是json格式时，数据插入失败
mysql> insert into user select null, 'test';
ERROR 3140 (22032): Invalid JSON text: "Invalid value." at position 1 in value for column 'user.data'.
mysql>
mysql> select * from user;
+----+-----------------------------------------------------------+
| id | data |
+----+-----------------------------------------------------------+
| 1 | {"age": 25, "name": "Chase", "email": "czhd2552@163.com"} |
| 2 | {"name": "Alisa", "address": "GuangZhou"} |
| 3 | {} |
| 4 | NULL |
+----+-----------------------------------------------------------+
4 rows in set (0.00 sec)
json类型的相关函数
-
json_append(5.7版本) -
json_array_append(8.0版本) json_contains_keyjson_extractjson_mergejson_removejson_replacejson_searchjson_setjson_test_parserjson_valid
mysql> select json_extract(data, '$.name'), json_extract(data, '$.email') from user;
+------------------------------+-------------------------------+
| json_extract(data, '$.name') | json_extract(data, '$.email') |
+------------------------------+-------------------------------+
| "Chase" | "czhd2552@163.com" |
| "Alisa" | NULL |
| NULL | NULL |
| NULL | NULL |
+------------------------------+-------------------------------+
4 rows in set (0.00 sec)
mysql>
mysql> select * from user where json_extract(data, '$.name') = 'Chase';
+----+-----------------------------------------------------------+
| id | data |
+----+-----------------------------------------------------------+
| 1 | {"age": 25, "name": "Chase", "email": "czhd2552@163.com"} |
+----+-----------------------------------------------------------+
1 row in set (0.00 sec)
mysql>
