前言
框架用的多了，已经不会写野生的SQL语句了，于是决定系统地阅读一下MySQL的官方文档。
常用类型比较
| 类型 | 范围 | 存储空间 | 备注 |
|---|---|---|---|
| BIT(M) | [1, 64]越界后默认值为1 | (M+7)/8 bytes | |
| TINYINT(M) | signed[-128, 127] unsigned[0, 255] | 1bytes | |
| SMALLINT(M) | signed[-32768, 32767] unsigned[0, 65535] | 2bytes | |
| MEDIUMINTINT(M) | signed[-8388608, 8388607] unsigned[0, 16777605] | 3bytes | |
| INT(M) | signed[-2147483648, 2147483647] unsigned[0, 4294967295] | 4bytes | |
| BIGINT(M) | signed[-9223372036854775808, 9223372036854775807] unsigned[0, 18446744073709551615] | 8bytes | |
| DECIMAL[(M[,D])] | [~ -1E+66, ~1E+66] | 8bytes | M数字的总数（精度），D是小数点后的数字（刻度）, M最大65，溢出后默认值为10，D最大30，溢出后默认值为0 |
| DOUBLE[(M[,D])] | [-1.7976931348623157E+308, 1.7976931348623157E+308] | 8bytes | |
| FLOAT[(p)] | [-3.402823466E+38,3.402823466E+38] | 4bytes, 0 <= p <= 24;8bytes, 25 <= p <= 53 | |
| CHAR(M) | 当0 <= M <= 255时为M × w bytes 其中w为指定字符集下每个字符的大小 | ||
| VARCHAR(M) | L + 1 bytes, L < =255;L + 2 bytes, L > 255 | ||
| TEXT | [0, 65535] | L + 2 bytes | |
| MEDIUMTEXT | [0, 167776150] | L + 3 bytes | |
| LONGTEXT | [0, 4294967295] | L + 4 bytes | |
| YEAR | [1901, 2155] | 1bytes | |
| DATE | [1000-01-01，9999-12-31] | 3bytes | |
| TIME | [-838:59:59, -838:59:59] | 3bytes | 5.6.4开始 5.6.4开始 3 bytes + fractional seconds storage |
| DATETIME | [1000-01-01 00:00:00, 9999-12-31 23:59:59] | 8bytes | 5.6.4开始 5 bytes + fractional seconds storage |
| TIMESTAMP | [1970-01-01 08:00:01, 2038-01-19 11:14:07] | 4bytes | 5.6.4开始 4 bytes + fractional seconds storage |
备注：5.6.4开始，时间类型支持微秒(最大6位)，所占的存储空间原来基础上加上微秒部分