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个人专栏:<数据结构>
<竞赛专栏>
<C语言> <C++>
<Linux> <OJ项目> <MySQL>
座右铭
悟已往之不谏，知来者之可追
前言
伴随着我们的知识的增长,有时候我们需要对用户的数据进行存储.
我们可以在我们当地的文件中存储文件,但是这样难免是过于复杂了,我们急需一种有效存储和读取数据的能力.
下面我们就展开我们数据库的学习之旅.
主流的数据库有很多:
- QL Sever： 微软的产品，.Net程序员的最爱，中大型项目。
- Oracle： 甲骨文产品，适合大型项目，复杂的业务逻辑，并发一般来说不如MySQL。 MySQL：世界上最受欢迎的数据库，属于甲骨文，并发性好，不适合做复杂的业务。主要用在电 商，SNS，论坛。对简单的SQL处理效果好。
- PostgreSQL :加州大学伯克利分校计算机系开发的关系型数据库，不管是私用，商用，还是学术研 究使用，可以免费使用，修改和分发。
- SQLite： 是一款轻型的数据库，是遵守ACID的关系型数据库管理系统，它包含在一个相对小的C库 中。它的设计目标是嵌入式的，而且目前已经在很多嵌入式产品中使用了它，它占用资源非常的 低，在嵌入式设备中，可能只需要几百K的内存就够了。
- H2： 是一个用Java开发的嵌入式数据库，它本身只是一个类库，可以直接嵌入到应用项目中。
而我们学习的就是MySQL
常用语句使用
创建数据库
CREATE DATABASE [IF NOT EXISTS] db_name [create_specification [, create_specification] …] create_specification: [DEFAULT] CHARACTER SET charset_name [DEFAULT] COLLATE collation_name
说明： 大写的表示关键字
[] 是可选项
CHARACTER SET: 指定数据库采用的字符集
COLLATE: 指定数据库字符集的校验规则
数据库的字符集和校验规则
什么是字符集?
什么是校验规则? 简单的了解就是:
我们可以类比日常生活中的交流:
假如我们现在需要和一个外国人进行交流的话,我们如果说的是普通话的话对方当然听不懂啊,
这是因为我们发出的信息是中文对方检验的规则是英文的.
那么有多少种的字符集和校验规则呢?
我们来查看一下
show collation;
+—————————–+———-+—–+———+———-+———+—————+
| Collation | Charset | Id | Default | Compiled | Sortlen | Pad_attribute |
+—————————–+———-+—–+———+———-+———+—————+
| armscii8_bin | armscii8 | 64 | | Yes | 1 | PAD SPACE |
| armscii8_general_ci | armscii8 | 32 | Yes | Yes | 1 | PAD SPACE |
| ascii_bin | ascii | 65 | | Yes | 1 | PAD SPACE |
| ascii_general_ci | ascii | 11 | Yes | Yes | 1 | PAD SPACE |
| big5_bin | big5 | 84 | | Yes | 1 | PAD SPACE |
| big5_chinese_ci | big5 | 1 | Yes | Yes | 1 | PAD SPACE |
| binary | binary | 63 | Yes | Yes | 1 | NO PAD |
| cp1250_bin | cp1250 | 66 | | Yes | 1 | PAD SPACE |
| cp1250_croatian_ci | cp1250 | 44 | | Yes | 1 | PAD SPACE |
| cp1250_czech_cs | cp1250 | 34 | | Yes | 2 | PAD SPACE |
| cp1250_general_ci | cp1250 | 26 | Yes | Yes | 1 | PAD SPACE |
| cp1250_polish_ci | cp1250 | 99 | | Yes | 1 | PAD SPACE |
| cp1251_bin | cp1251 | 50 | | Yes | 1 | PAD SPACE |
| cp1251_bulgarian_ci | cp1251 | 14 | | Yes | 1 | PAD SPACE |
| cp1251_general_ci | cp1251 | 51 | Yes | Yes | 1 | PAD SPACE |
| cp1251_general_cs | cp1251 | 52 | | Yes | 1 | PAD SPACE |
| cp1251_ukrainian_ci | cp1251 | 23 | | Yes | 1 | PAD SPACE |
| cp1256_bin | cp1256 | 67 | | Yes | 1 | PAD SPACE |
| cp1256_general_ci | cp1256 | 57 | Yes | Yes | 1 | PAD SPACE |
| cp1257_bin | cp1257 | 58 | | Yes | 1 | PAD SPACE |
| cp1257_general_ci | cp1257 | 59 | Yes | Yes | 1 | PAD SPACE |
| cp1257_lithuanian_ci | cp1257 | 29 | | Yes | 1 | PAD SPACE |
| cp850_bin | cp850 | 80 | | Yes | 1 | PAD SPACE |
| cp850_general_ci | cp850 | 4 | Yes | Yes | 1 | PAD SPACE |
| cp852_bin | cp852 | 81 | | Yes | 1 | PAD SPACE |
| cp852_general_ci | cp852 | 40 | Yes | Yes | 1 | PAD SPACE |
| cp866_bin | cp866 | 68 | | Yes | 1 | PAD SPACE |
| cp866_general_ci | cp866 | 36 | Yes | Yes | 1 | PAD SPACE |
| cp932_bin | cp932 | 96 | | Yes | 1 | PAD SPACE |
| cp932_japanese_ci | cp932 | 95 | Yes | Yes | 1 | PAD SPACE |
| dec8_bin | dec8 | 69 | | Yes | 1 | PAD SPACE |
| dec8_swedish_ci | dec8 | 3 | Yes | Yes | 1 | PAD SPACE |
| eucjpms_bin | eucjpms | 98 | | Yes | 1 | PAD SPACE |
| eucjpms_japanese_ci | eucjpms | 97 | Yes | Yes | 1 | PAD SPACE |
| euckr_bin | euckr | 85 | | Yes | 1 | PAD SPACE |
| euckr_korean_ci | euckr | 19 | Yes | Yes | 1 | PAD SPACE |
| gb18030_bin | gb18030 | 249 | | Yes | 1 | PAD SPACE |
| gb18030_chinese_ci | gb18030 | 248 | Yes | Yes | 2 | PAD SPACE |
| gb18030_unicode_520_ci | gb18030 | 250 | | Yes | 8 | PAD SPACE |
| gb2312_bin | gb2312 | 86 | | Yes | 1 | PAD SPACE |
| gb2312_chinese_ci | gb2312 | 24 | Yes | Yes | 1 | PAD SPACE |
| gbk_bin | gbk | 87 | | Yes | 1 | PAD SPACE |
| gbk_chinese_ci | gbk | 28 | Yes | Yes | 1 | PAD SPACE |
| geostd8_bin | geostd8 | 93 | | Yes | 1 | PAD SPACE |
| geostd8_general_ci | geostd8 | 92 | Yes | Yes | 1 | PAD SPACE |
| greek_bin | greek | 70 | | Yes | 1 | PAD SPACE |
| greek_general_ci | greek | 25 | Yes | Yes | 1 | PAD SPACE |
| hebrew_bin | hebrew | 71 | | Yes | 1 | PAD SPACE |
| hebrew_general_ci | hebrew | 16 | Yes | Yes | 1 | PAD SPACE |
| hp8_bin | hp8 | 72 | | Yes | 1 | PAD SPACE |
| hp8_english_ci | hp8 | 6 | Yes | Yes | 1 | PAD SPACE |
| keybcs2_bin | keybcs2 | 73 | | Yes | 1 | PAD SPACE |
| keybcs2_general_ci | keybcs2 | 37 | Yes | Yes | 1 | PAD SPACE |
| koi8r_bin | koi8r | 74 | | Yes | 1 | PAD SPACE |
| koi8r_general_ci | koi8r | 7 | Yes | Yes | 1 | PAD SPACE |
| koi8u_bin | koi8u | 75 | | Yes | 1 | PAD SPACE |
| koi8u_general_ci | koi8u | 22 | Yes | Yes | 1 | PAD SPACE |
| latin1_bin | latin1 | 47 | | Yes | 1 | PAD SPACE |
| latin1_danish_ci | latin1 | 15 | | Yes | 1 | PAD SPACE |
| latin1_general_ci | latin1 | 48 | | Yes | 1 | PAD SPACE |
| latin1_general_cs | latin1 | 49 | | Yes | 1 | PAD SPACE |
| latin1_german1_ci | latin1 | 5 | | Yes | 1 | PAD SPACE |
| latin1_german2_ci | latin1 | 31 | | Yes | 2 | PAD SPACE |
| latin1_spanish_ci | latin1 | 94 | | Yes | 1 | PAD SPACE |
| latin1_swedish_ci | latin1 | 8 | Yes | Yes | 1 | PAD SPACE |
| latin2_bin | latin2 | 77 | | Yes | 1 | PAD SPACE |
| latin2_croatian_ci | latin2 | 27 | | Yes | 1 | PAD SPACE |
| latin2_czech_cs | latin2 | 2 | | Yes | 4 | PAD SPACE |
| latin2_general_ci | latin2 | 9 | Yes | Yes | 1 | PAD SPACE |
| latin2_hungarian_ci | latin2 | 21 | | Yes | 1 | PAD SPACE |
| latin5_bin | latin5 | 78 | | Yes | 1 | PAD SPACE |
| latin5_turkish_ci | latin5 | 30 | Yes | Yes | 1 | PAD SPACE |
| latin7_bin | latin7 | 79 | | Yes | 1 | PAD SPACE |
| latin7_estonian_cs | latin7 | 20 | | Yes | 1 | PAD SPACE |
| latin7_general_ci | latin7 | 41 | Yes | Yes | 1 | PAD SPACE |
| latin7_general_cs | latin7 | 42 | | Yes | 1 | PAD SPACE |
| macce_bin | macce | 43 | | Yes | 1 | PAD SPACE |
| macce_general_ci | macce | 38 | Yes | Yes | 1 | PAD SPACE |
| macroman_bin | macroman | 53 | | Yes | 1 | PAD SPACE |
| macroman_general_ci | macroman | 39 | Yes | Yes | 1 | PAD SPACE |
| sjis_bin | sjis | 88 | | Yes | 1 | PAD SPACE |
| sjis_japanese_ci | sjis | 13 | Yes | Yes | 1 | PAD SPACE |
| swe7_bin | swe7 | 82 | | Yes | 1 | PAD SPACE |
| swe7_swedish_ci | swe7 | 10 | Yes | Yes | 1 | PAD SPACE |
| tis620_bin | tis620 | 89 | | Yes | 1 | PAD SPACE |
| tis620_thai_ci | tis620 | 18 | Yes | Yes | 4 | PAD SPACE |
| ucs2_bin | ucs2 | 90 | | Yes | 1 | PAD SPACE |
| ucs2_croatian_ci | ucs2 | 149 | | Yes | 8 | PAD SPACE |
| ucs2_czech_ci | ucs2 | 138 | | Yes | 8 | PAD SPACE |
| ucs2_danish_ci | ucs2 | 139 | | Yes | 8 | PAD SPACE |
| ucs2_esperanto_ci | ucs2 | 145 | | Yes | 8 | PAD SPACE |
| ucs2_estonian_ci | ucs2 | 134 | | Yes | 8 | PAD SPACE |
| ucs2_general_ci | ucs2 | 35 | Yes | Yes | 1 | PAD SPACE |
| ucs2_general_mysql500_ci | ucs2 | 159 | | Yes | 1 | PAD SPACE |
| ucs2_german2_ci | ucs2 | 148 | | Yes | 8 | PAD SPACE |
| ucs2_hungarian_ci | ucs2 | 146 | | Yes | 8 | PAD SPACE |
| ucs2_icelandic_ci | ucs2 | 129 | | Yes | 8 | PAD SPACE |
| ucs2_latvian_ci | ucs2 | 130 | | Yes | 8 | PAD SPACE |
| ucs2_lithuanian_ci | ucs2 | 140 | | Yes | 8 | PAD SPACE |
| ucs2_persian_ci | ucs2 | 144 | | Yes | 8 | PAD SPACE |
| ucs2_polish_ci | ucs2 | 133 | | Yes | 8 | PAD SPACE |
| ucs2_romanian_ci | ucs2 | 131 | | Yes | 8 | PAD SPACE |
| ucs2_roman_ci | ucs2 | 143 | | Yes | 8 | PAD SPACE |
| ucs2_sinhala_ci | ucs2 | 147 | | Yes | 8 | PAD SPACE |
| ucs2_slovak_ci | ucs2 | 141 | | Yes | 8 | PAD SPACE |
| ucs2_slovenian_ci | ucs2 | 132 | | Yes | 8 | PAD SPACE |
| ucs2_spanish2_ci | ucs2 | 142 | | Yes | 8 | PAD SPACE |
| ucs2_spanish_ci | ucs2 | 135 | | Yes | 8 | PAD SPACE |
| ucs2_swedish_ci | ucs2 | 136 | | Yes | 8 | PAD SPACE |
| ucs2_turkish_ci | ucs2 | 137 | | Yes | 8 | PAD SPACE |
| ucs2_unicode_520_ci | ucs2 | 150 | | Yes | 8 | PAD SPACE |
| ucs2_unicode_ci | ucs2 | 128 | | Yes | 8 | PAD SPACE |
| ucs2_vietnamese_ci | ucs2 | 151 | | Yes | 8 | PAD SPACE |
| ujis_bin | ujis | 91 | | Yes | 1 | PAD SPACE |
| ujis_japanese_ci | ujis | 12 | Yes | Yes | 1 | PAD SPACE |
| utf16le_bin | utf16le | 62 | | Yes | 1 | PAD SPACE |
| utf16le_general_ci | utf16le | 56 | Yes | Yes | 1 | PAD SPACE |
| utf16_bin | utf16 | 55 | | Yes | 1 | PAD SPACE |
| utf16_croatian_ci | utf16 | 122 | | Yes | 8 | PAD SPACE |
| utf16_czech_ci | utf16 | 111 | | Yes | 8 | PAD SPACE |
| utf16_danish_ci | utf16 | 112 | | Yes | 8 | PAD SPACE |
| utf16_esperanto_ci | utf16 | 118 | | Yes | 8 | PAD SPACE |
| utf16_estonian_ci | utf16 | 107 | | Yes | 8 | PAD SPACE |
| utf16_general_ci | utf16 | 54 | Yes | Yes | 1 | PAD SPACE |
| utf16_german2_ci | utf16 | 121 | | Yes | 8 | PAD SPACE |
| utf16_hungarian_ci | utf16 | 119 | | Yes | 8 | PAD SPACE |
| utf16_icelandic_ci | utf16 | 102 | | Yes | 8 | PAD SPACE |
| utf16_latvian_ci | utf16 | 103 | | Yes | 8 | PAD SPACE |
| utf16_lithuanian_ci | utf16 | 113 | | Yes | 8 | PAD SPACE |
| utf16_persian_ci | utf16 | 117 | | Yes | 8 | PAD SPACE |
| utf16_polish_ci | utf16 | 106 | | Yes | 8 | PAD SPACE |
| utf16_romanian_ci | utf16 | 104 | | Yes | 8 | PAD SPACE |
| utf16_roman_ci | utf16 | 116 | | Yes | 8 | PAD SPACE |
| utf16_sinhala_ci | utf16 | 120 | | Yes | 8 | PAD SPACE |
| utf16_slovak_ci | utf16 | 114 | | Yes | 8 | PAD SPACE |
| utf16_slovenian_ci | utf16 | 105 | | Yes | 8 | PAD SPACE |
| utf16_spanish2_ci | utf16 | 115 | | Yes | 8 | PAD SPACE |
| utf16_spanish_ci | utf16 | 108 | | Yes | 8 | PAD SPACE |
| utf16_swedish_ci | utf16 | 109 | | Yes | 8 | PAD SPACE |
| utf16_turkish_ci | utf16 | 110 | | Yes | 8 | PAD SPACE |
| utf16_unicode_520_ci | utf16 | 123 | | Yes | 8 | PAD SPACE |
| utf16_unicode_ci | utf16 | 101 | | Yes | 8 | PAD SPACE |
| utf16_vietnamese_ci | utf16 | 124 | | Yes | 8 | PAD SPACE |
| utf32_bin | utf32 | 61 | | Yes | 1 | PAD SPACE |
| utf32_croatian_ci | utf32 | 181 | | Yes | 8 | PAD SPACE |
| utf32_czech_ci | utf32 | 170 | | Yes | 8 | PAD SPACE |
| utf32_danish_ci | utf32 | 171 | | Yes | 8 | PAD SPACE |
| utf32_esperanto_ci | utf32 | 177 | | Yes | 8 | PAD SPACE |
| utf32_estonian_ci | utf32 | 166 | | Yes | 8 | PAD SPACE |
| utf32_general_ci | utf32 | 60 | Yes | Yes | 1 | PAD SPACE |
| utf32_german2_ci | utf32 | 180 | | Yes | 8 | PAD SPACE |
| utf32_hungarian_ci | utf32 | 178 | | Yes | 8 | PAD SPACE |
| utf32_icelandic_ci | utf32 | 161 | | Yes | 8 | PAD SPACE |
| utf32_latvian_ci | utf32 | 162 | | Yes | 8 | PAD SPACE |
| utf32_lithuanian_ci | utf32 | 172 | | Yes | 8 | PAD SPACE |
| utf32_persian_ci | utf32 | 176 | | Yes | 8 | PAD SPACE |
| utf32_polish_ci | utf32 | 165 | | Yes | 8 | PAD SPACE |
| utf32_romanian_ci | utf32 | 163 | | Yes | 8 | PAD SPACE |
| utf32_roman_ci | utf32 | 175 | | Yes | 8 | PAD SPACE |
| utf32_sinhala_ci | utf32 | 179 | | Yes | 8 | PAD SPACE |
| utf32_slovak_ci | utf32 | 173 | | Yes | 8 | PAD SPACE |
| utf32_slovenian_ci | utf32 | 164 | | Yes | 8 | PAD SPACE |
| utf32_spanish2_ci | utf32 | 174 | | Yes | 8 | PAD SPACE |
| utf32_spanish_ci | utf32 | 167 | | Yes | 8 | PAD SPACE |
| utf32_swedish_ci | utf32 | 168 | | Yes | 8 | PAD SPACE |
| utf32_turkish_ci | utf32 | 169 | | Yes | 8 | PAD SPACE |
| utf32_unicode_520_ci | utf32 | 182 | | Yes | 8 | PAD SPACE |
| utf32_unicode_ci | utf32 | 160 | | Yes | 8 | PAD SPACE |
| utf32_vietnamese_ci | utf32 | 183 | | Yes | 8 | PAD SPACE |
| utf8mb3_bin | utf8mb3 | 83 | | Yes | 1 | PAD SPACE |
| utf8mb3_croatian_ci | utf8mb3 | 213 | | Yes | 8 | PAD SPACE |
| utf8mb3_czech_ci | utf8mb3 | 202 | | Yes | 8 | PAD SPACE |
| utf8mb3_danish_ci | utf8mb3 | 203 | | Yes | 8 | PAD SPACE |
| utf8mb3_esperanto_ci | utf8mb3 | 209 | | Yes | 8 | PAD SPACE |
| utf8mb3_estonian_ci | utf8mb3 | 198 | | Yes | 8 | PAD SPACE |
| utf8mb3_general_ci | utf8mb3 | 33 | Yes | Yes | 1 | PAD SPACE |
| utf8mb3_general_mysql500_ci | utf8mb3 | 223 | | Yes | 1 | PAD SPACE |
| utf8mb3_german2_ci | utf8mb3 | 212 | | Yes | 8 | PAD SPACE |
| utf8mb3_hungarian_ci | utf8mb3 | 210 | | Yes | 8 | PAD SPACE |
| utf8mb3_icelandic_ci | utf8mb3 | 193 | | Yes | 8 | PAD SPACE |
| utf8mb3_latvian_ci | utf8mb3 | 194 | | Yes | 8 | PAD SPACE |
| utf8mb3_lithuanian_ci | utf8mb3 | 204 | | Yes | 8 | PAD SPACE |
| utf8mb3_persian_ci | utf8mb3 | 208 | | Yes | 8 | PAD SPACE |
| utf8mb3_polish_ci | utf8mb3 | 197 | | Yes | 8 | PAD SPACE |
| utf8mb3_romanian_ci | utf8mb3 | 195 | | Yes | 8 | PAD SPACE |
| utf8mb3_roman_ci | utf8mb3 | 207 | | Yes | 8 | PAD SPACE |
| utf8mb3_sinhala_ci | utf8mb3 | 211 | | Yes | 8 | PAD SPACE |
| utf8mb3_slovak_ci | utf8mb3 | 205 | | Yes | 8 | PAD SPACE |
| utf8mb3_slovenian_ci | utf8mb3 | 196 | | Yes | 8 | PAD SPACE |
| utf8mb3_spanish2_ci | utf8mb3 | 206 | | Yes | 8 | PAD SPACE |
| utf8mb3_spanish_ci | utf8mb3 | 199 | | Yes | 8 | PAD SPACE |
| utf8mb3_swedish_ci | utf8mb3 | 200 | | Yes | 8 | PAD SPACE |
| utf8mb3_tolower_ci | utf8mb3 | 76 | | Yes | 1 | PAD SPACE |
| utf8mb3_turkish_ci | utf8mb3 | 201 | | Yes | 8 | PAD SPACE |
| utf8mb3_unicode_520_ci | utf8mb3 | 214 | | Yes | 8 | PAD SPACE |
| utf8mb3_unicode_ci | utf8mb3 | 192 | | Yes | 8 | PAD SPACE |
| utf8mb3_vietnamese_ci | utf8mb3 | 215 | | Yes | 8 | PAD SPACE |
| utf8mb4_0900_ai_ci | utf8mb4 | 255 | Yes | Yes | 0 | NO PAD |
| utf8mb4_0900_as_ci | utf8mb4 | 305 | | Yes | 0 | NO PAD |
| utf8mb4_0900_as_cs | utf8mb4 | 278 | | Yes | 0 | NO PAD |
| utf8mb4_0900_bin | utf8mb4 | 309 | | Yes | 1 | NO PAD |
| utf8mb4_bg_0900_ai_ci | utf8mb4 | 318 | | Yes | 0 | NO PAD |
| utf8mb4_bg_0900_as_cs | utf8mb4 | 319 | | Yes | 0 | NO PAD |
| utf8mb4_bin | utf8mb4 | 46 | | Yes | 1 | PAD SPACE |
| utf8mb4_bs_0900_ai_ci | utf8mb4 | 316 | | Yes | 0 | NO PAD |
| utf8mb4_bs_0900_as_cs | utf8mb4 | 317 | | Yes | 0 | NO PAD |
| utf8mb4_croatian_ci | utf8mb4 | 245 | | Yes | 8 | PAD SPACE |
| utf8mb4_cs_0900_ai_ci | utf8mb4 | 266 | | Yes | 0 | NO PAD |
| utf8mb4_cs_0900_as_cs | utf8mb4 | 289 | | Yes | 0 | NO PAD |
| utf8mb4_czech_ci | utf8mb4 | 234 | | Yes | 8 | PAD SPACE |
| utf8mb4_danish_ci | utf8mb4 | 235 | | Yes | 8 | PAD SPACE |
| utf8mb4_da_0900_ai_ci | utf8mb4 | 267 | | Yes | 0 | NO PAD |
| utf8mb4_da_0900_as_cs | utf8mb4 | 290 | | Yes | 0 | NO PAD |
| utf8mb4_de_pb_0900_ai_ci | utf8mb4 | 256 | | Yes | 0 | NO PAD |
| utf8mb4_de_pb_0900_as_cs | utf8mb4 | 279 | | Yes | 0 | NO PAD |
| utf8mb4_eo_0900_ai_ci | utf8mb4 | 273 | | Yes | 0 | NO PAD |
| utf8mb4_eo_0900_as_cs | utf8mb4 | 296 | | Yes | 0 | NO PAD |
| utf8mb4_esperanto_ci | utf8mb4 | 241 | | Yes | 8 | PAD SPACE |
| utf8mb4_estonian_ci | utf8mb4 | 230 | | Yes | 8 | PAD SPACE |
| utf8mb4_es_0900_ai_ci | utf8mb4 | 263 | | Yes | 0 | NO PAD |
| utf8mb4_es_0900_as_cs | utf8mb4 | 286 | | Yes | 0 | NO PAD |
| utf8mb4_es_trad_0900_ai_ci | utf8mb4 | 270 | | Yes | 0 | NO PAD |
| utf8mb4_es_trad_0900_as_cs | utf8mb4 | 293 | | Yes | 0 | NO PAD |
| utf8mb4_et_0900_ai_ci | utf8mb4 | 262 | | Yes | 0 | NO PAD |
| utf8mb4_et_0900_as_cs | utf8mb4 | 285 | | Yes | 0 | NO PAD |
| utf8mb4_general_ci | utf8mb4 | 45 | | Yes | 1 | PAD SPACE |
| utf8mb4_german2_ci | utf8mb4 | 244 | | Yes | 8 | PAD SPACE |
| utf8mb4_gl_0900_ai_ci | utf8mb4 | 320 | | Yes | 0 | NO PAD |
| utf8mb4_gl_0900_as_cs | utf8mb4 | 321 | | Yes | 0 | NO PAD |
| utf8mb4_hr_0900_ai_ci | utf8mb4 | 275 | | Yes | 0 | NO PAD |
| utf8mb4_hr_0900_as_cs | utf8mb4 | 298 | | Yes | 0 | NO PAD |
| utf8mb4_hungarian_ci | utf8mb4 | 242 | | Yes | 8 | PAD SPACE |
| utf8mb4_hu_0900_ai_ci | utf8mb4 | 274 | | Yes | 0 | NO PAD |
| utf8mb4_hu_0900_as_cs | utf8mb4 | 297 | | Yes | 0 | NO PAD |
| utf8mb4_icelandic_ci | utf8mb4 | 225 | | Yes | 8 | PAD SPACE |
| utf8mb4_is_0900_ai_ci | utf8mb4 | 257 | | Yes | 0 | NO PAD |
| utf8mb4_is_0900_as_cs | utf8mb4 | 280 | | Yes | 0 | NO PAD |
| utf8mb4_ja_0900_as_cs | utf8mb4 | 303 | | Yes | 0 | NO PAD |
| utf8mb4_ja_0900_as_cs_ks | utf8mb4 | 304 | | Yes | 24 | NO PAD |
| utf8mb4_latvian_ci | utf8mb4 | 226 | | Yes | 8 | PAD SPACE |
| utf8mb4_la_0900_ai_ci | utf8mb4 | 271 | | Yes | 0 | NO PAD |
| utf8mb4_la_0900_as_cs | utf8mb4 | 294 | | Yes | 0 | NO PAD |
| utf8mb4_lithuanian_ci | utf8mb4 | 236 | | Yes | 8 | PAD SPACE |
| utf8mb4_lt_0900_ai_ci | utf8mb4 | 268 | | Yes | 0 | NO PAD |
| utf8mb4_lt_0900_as_cs | utf8mb4 | 291 | | Yes | 0 | NO PAD |
| utf8mb4_lv_0900_ai_ci | utf8mb4 | 258 | | Yes | 0 | NO PAD |
| utf8mb4_lv_0900_as_cs | utf8mb4 | 281 | | Yes | 0 | NO PAD |
| utf8mb4_mn_cyrl_0900_ai_ci | utf8mb4 | 322 | | Yes | 0 | NO PAD |
| utf8mb4_mn_cyrl_0900_as_cs | utf8mb4 | 323 | | Yes | 0 | NO PAD |
| utf8mb4_nb_0900_ai_ci | utf8mb4 | 310 | | Yes | 0 | NO PAD |
| utf8mb4_nb_0900_as_cs | utf8mb4 | 311 | | Yes | 0 | NO PAD |
| utf8mb4_nn_0900_ai_ci | utf8mb4 | 312 | | Yes | 0 | NO PAD |
| utf8mb4_nn_0900_as_cs | utf8mb4 | 313 | | Yes | 0 | NO PAD |
| utf8mb4_persian_ci | utf8mb4 | 240 | | Yes | 8 | PAD SPACE |
| utf8mb4_pl_0900_ai_ci | utf8mb4 | 261 | | Yes | 0 | NO PAD |
| utf8mb4_pl_0900_as_cs | utf8mb4 | 284 | | Yes | 0 | NO PAD |
| utf8mb4_polish_ci | utf8mb4 | 229 | | Yes | 8 | PAD SPACE |
| utf8mb4_romanian_ci | utf8mb4 | 227 | | Yes | 8 | PAD SPACE |
| utf8mb4_roman_ci | utf8mb4 | 239 | | Yes | 8 | PAD SPACE |
| utf8mb4_ro_0900_ai_ci | utf8mb4 | 259 | | Yes | 0 | NO PAD |
| utf8mb4_ro_0900_as_cs | utf8mb4 | 282 | | Yes | 0 | NO PAD |
| utf8mb4_ru_0900_ai_ci | utf8mb4 | 306 | | Yes | 0 | NO PAD |
| utf8mb4_ru_0900_as_cs | utf8mb4 | 307 | | Yes | 0 | NO PAD |
| utf8mb4_sinhala_ci | utf8mb4 | 243 | | Yes | 8 | PAD SPACE |
| utf8mb4_sk_0900_ai_ci | utf8mb4 | 269 | | Yes | 0 | NO PAD |
| utf8mb4_sk_0900_as_cs | utf8mb4 | 292 | | Yes | 0 | NO PAD |
| utf8mb4_slovak_ci | utf8mb4 | 237 | | Yes | 8 | PAD SPACE |
| utf8mb4_slovenian_ci | utf8mb4 | 228 | | Yes | 8 | PAD SPACE |
| utf8mb4_sl_0900_ai_ci | utf8mb4 | 260 | | Yes | 0 | NO PAD |
| utf8mb4_sl_0900_as_cs | utf8mb4 | 283 | | Yes | 0 | NO PAD |
| utf8mb4_spanish2_ci | utf8mb4 | 238 | | Yes | 8 | PAD SPACE |
| utf8mb4_spanish_ci | utf8mb4 | 231 | | Yes | 8 | PAD SPACE |
| utf8mb4_sr_latn_0900_ai_ci | utf8mb4 | 314 | | Yes | 0 | NO PAD |
| utf8mb4_sr_latn_0900_as_cs | utf8mb4 | 315 | | Yes | 0 | NO PAD |
| utf8mb4_sv_0900_ai_ci | utf8mb4 | 264 | | Yes | 0 | NO PAD |
| utf8mb4_sv_0900_as_cs | utf8mb4 | 287 | | Yes | 0 | NO PAD |
| utf8mb4_swedish_ci | utf8mb4 | 232 | | Yes | 8 | PAD SPACE |
| utf8mb4_tr_0900_ai_ci | utf8mb4 | 265 | | Yes | 0 | NO PAD |
| utf8mb4_tr_0900_as_cs | utf8mb4 | 288 | | Yes | 0 | NO PAD |
| utf8mb4_turkish_ci | utf8mb4 | 233 | | Yes | 8 | PAD SPACE |
| utf8mb4_unicode_520_ci | utf8mb4 | 246 | | Yes | 8 | PAD SPACE |
| utf8mb4_unicode_ci | utf8mb4 | 224 | | Yes | 8 | PAD SPACE |
| utf8mb4_vietnamese_ci | utf8mb4 | 247 | | Yes | 8 | PAD SPACE |
| utf8mb4_vi_0900_ai_ci | utf8mb4 | 277 | | Yes | 0 | NO PAD |
| utf8mb4_vi_0900_as_cs | utf8mb4 | 300 | | Yes | 0 | NO PAD |
| utf8mb4_zh_0900_as_cs | utf8mb4 | 308 | | Yes | 0 | NO PAD |
+—————————–+———-+—–+———+———-+———+—————+
需要知道的是我们创建出来的数据库默认的字符集是utf8，校验规则 是：utf8_ general_ ci
那么我们来验证不同的校验规则对我们存储的数据有什么影响
create database test1 collate utf8_general_ci;
create table person(name varchar(20));
insert into person values('a');
insert into person values('A');
insert into person values('b');
insert into person values('B');
create database test2 collate utf8_bin;
create table person(name varchar(20));
insert into person values('a');
insert into person values('A');
insert into person values('b');
insert into person values('B');
use test1;
select * from person where name='a';
在第一个表中查询的结果是
在第二个数据库中的结果却改变了
这是因为两个数据库地校验规则不同
第一个数据库，校验规则使用utf8_ general_ ci[不区分大小写]
第二个数据库用的校验规则而是区分大小写的
修改数据库
语法就是ALTER DATABASE db_name;
在针对于数据库的修改的操作中,我们修改的一般就是数据库的字符集和校验规则.
删除数据库
语法DROP DATABASE [IF EXISTS] db_ name;
需要注意的就是我们一旦对数据库进行了删除的话,数据库中所有的数据都会消失
展示所有的数据库
show databases;
使用指定的数据库
use 数据库名称
查看当前所处于的数据库的名称
select database();
