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This article introduces how to use DATE to achieve data type storage in MYSQL, the content is very detailed, interested friends can refer to, hope to be helpful to you.

MYSQL- data type storage-DATE on Engine of myisam [@ more@]

1. Environment version:

OS: LINUX AS4

MYSQL: 5.0.51a-log

ENGINE: Myisam DEFAULT CHARSET=latin1

two。 Analysis.

The date type occupies 3 bytes (24 bits), ranging from '1000-01-01' to '9999-12-31' in the format 'YYYY-MM-DD'

Where: from left to right

1x 15 bits: storage year (15 bits in total)

16-19 bits: storage month (4 digits in total)

2024-bit: storage day (5 bits in total)

For example, "2009-03-09", where:

Decimal hexadecimal binary

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2009-> 0X7D9-> 000 0111 1101 1001

03-> 0X03-> 0011

09-> 0X09-> 01001

-

After combining the binary system: 0000 1111 1011 0010 0110 1001

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0 F B 2 6 9

Hexadecimal: 0FB269

Note: the data in the date field is stored in reverse.

3. Verification

Here's what we can verify:

Drop table if exists heyf

Create table heyf (id int, birthday date) type myisam DEFAULT CHARSET=latin1

Insert into heyf values (12 months 2009-03-09')

System hexdump / opt/mysql/data/test/heyf.MYD

-

0000000 0cf9 0000 6900 0fb2

0000008

-

Where:

F9: marker bit

0C 00 00 00: COL1, INT = 12

69b20f: the date. Because it is reverse storage, it needs to be read in reverse: 0FB269

4. Correlation function

4.1 convert hexadecimal to decimal

Select 0xa + 0

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ten

Or

Select conv ("a", 16,510)

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ten

4.2 convert decimal to hexadecimal

Select conv (10, 10, 10, 16)

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A

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