MySQL筆記之數據類型詳解。本站提示廣大學習愛好者：（MySQL筆記之數據類型詳解）文章只能為提供參考，不一定能成為您想要的結果。以下是MySQL筆記之數據類型詳解正文
字符型數據
字符型數據可使用定長或變長的字符串來完成，其分歧點在於固定長度的字符串應用空格向右填充，以包管占用異樣的字節數;變長字符串不須要向右填充，而且一切字節數可變。
char 定長型，字節長度固定，最年夜長度為255字節，可使用char（20）這類方法限制長度，查詢速度快，但不靈巧
varchar 變長型，字節長度隨數據質變化，最多可存儲65535字節，varchar（20）可以限制長度，查詢速度不及char，但應用靈巧
假如須要存儲文本或許文檔，須要應用text類型數據，包含四種
tinytext 255字節
text 65535字節
mediumtext 16777215字節
longtext 4294967295字節
以上三種在停止分組排序或許比擬的時刻只采取前1024字節停止比擬
字符集
關於拉丁語系，好比英語，個中每一個字母只須要1個字節來存儲;而其他一些說話，好比中文，包括了年夜量字符，每一個字符的存儲須要多個字節，是以這類字符集被稱為多字符集
在mysql中，可使用SHOW CAHRACTER SET語句檢查字符集
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 |
| 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 |
+----------+-----------------------------+---------------------+--------+
rows in set (0.00 sec)
個中Maxlen列年夜於1則代表此行動多字符集，好比gb2312,存儲一個漢字最多須要2個字節，utf8最多則須要3個
數值型數據
整數型數據
浮點型數據
數值型數據可以界說為unsigned，對整數罷了可以轉變其規模，對浮點數而言可以限制其不克不及為正數
時光數據
