数字类型

On 32-bit platforms, the maximum useful value for unix_timestamp is 2147483647.999999, which returns '2038-01-19 03:14:07.999999' UTC. On 64-bit platforms, the effective maximum is 32536771199.999999, which returns '3001-01-18 23:59:59.999999' UTC. Regardless of platform or version, a greater value for unix_timestamp than the effective maximum returns 0.

Date and Time Type Storage Requirements

For TIME, DATETIME, and TIMESTAMP columns, the storage required for tables created before MySQL 5.6.4 differs from tables created from 5.6.4 on. This is due to a change in 5.6.4 that permits these types to have a fractional part, which requires from 0 to 3 bytes.

Data Type	Storage Required Before MySQL 5.6.4	Storage Required as of MySQL 5.6.4
YEAR	1 byte	1 byte
DATE	3 bytes	3 bytes
TIME	3 bytes	3 bytes + fractional seconds storage
DATETIME	8 bytes	5 bytes + fractional seconds storage
TIMESTAMP	4 bytes	4 bytes + fractional seconds storage

As of MySQL 5.6.4, storage for YEAR and DATE remains unchanged. However, TIME, DATETIME, and TIMESTAMP are represented differently. DATETIME is packed more efficiently, requiring 5 rather than 8 bytes for the nonfractional part, and all three parts have a fractional part that requires from 0 to 3 bytes, depending on the fractional seconds precision of stored values.

Fractional Seconds Precision	Storage Required
0	0 bytes
1, 2	1 byte
3, 4	2 bytes
5, 6	3 bytes

For example, TIME(0), TIME(2), TIME(4), and TIME(6) use 3, 4, 5, and 6 bytes, respectively. TIME and TIME(0) are equivalent and require the same storage.

For details about internal representation of temporal values, see MySQL Internals: Important Algorithms and Structures.

字符串类型：COLLATION

日期类型

非结构存储

表结构设计-忘记范式

表压缩

SQL or NoSQL

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