存儲空間消耗磁盤比較 int varchar date
小結:
1、日期類型按照date存儲節省空間,僅3字節,而按照字符串型char 8字節 20190316 , varchar 20190316 9字節;
2、對於小於32768的整數,按照smallint僅僅為2字節,較字符型節約空間;
3、時間戳 1552187447 用int ,而非char(12);整數ip,長ip,用bigint;能數字,不字符型;
2019-03-16 20190316
https://dev.mysql.com/doc/refman/8.0/en/integer-types.html
Table 11.1 Required Storage and Range for Integer Types Supported by MySQL
Type | Storage (Bytes) | Minimum Value Signed | Minimum Value Unsigned | Maximum Value Signed | Maximum Value Unsigned |
---|---|---|---|---|---|
TINYINT |
1 | -128 |
0 |
127 |
255 |
SMALLINT |
2 | -32768 |
0 |
32767 |
65535 |
MEDIUMINT |
3 | -8388608 |
0 |
8388607 |
16777215 |
INT |
4 | -2147483648 |
0 |
2147483647 |
4294967295 |
BIGINT |
8 | -263 |
0 |
263-1 |
264-1 |
>>> 2**32
4294967296
>>> 2**31
2147483648
>>>
>>> 2**15
32768
>>>
https://dev.mysql.com/doc/refman/8.0/en/char.html
Value | CHAR(4) | Storage Required | VARCHAR(4) | Storage Required |
---|---|---|---|---|
‘‘ |
‘ ‘ |
4 bytes | ‘‘ |
1 byte |
‘ab‘ |
‘ab ‘ |
4 bytes | ‘ab‘ |
3 bytes |
‘abcd‘ |
‘abcd‘ |
4 bytes | ‘abcd‘ |
5 bytes |
‘abcdefgh‘ |
‘abcd‘ |
4 bytes | ‘abcd‘ |
5 bytes |
The values shown as stored in the last row of the table apply only when not using strict mode; if MySQL is running in strict mode, values that exceed the column length are not stored, and an error results.
https://dev.mysql.com/doc/refman/8.0/en/storage-requirements.html#data-types-storage-reqs-date-time
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
, andTIMESTAMP
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
andTIME(0)
are equivalent and require the same storage.
存儲空間消耗磁盤比較 int varchar date