Database Add Time Type

Date Type:

DateTime date hour minute seconds format must be

' Yyyy-mm-dd hh:mm:ss '

Timestamp type:

What is a timestamp, is a date, if you have the year, month, day, hour, minute, second, is the timestamp.

Change the type of T1 table to timestamp

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Value range: 1970 1 1 00:00:00 But we're in the East 8, so when we test, the minimum time to add is "1970-1-108:00:01"

Date type: Only month day

Time type: only seconds and minutes

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Year type, can only be stored for years:

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Places to note about dates:

1. In the database, the date plus the number, the number

2. In the database, numbers + numbers, numbers

3. In the database, numbers + strings, numbers

4. In the database, the string + string, the number, at this time if the string can not become a number, as far as possible to become a number;

String type:

The char string type char (n) indicates that the string holds a maximum of n bytes.

VarChar is also a string type, and varchar (n) is also a means of storing up to n bytes. This effect, like char, they are always a little different!

Char is a fixed length

VARCHAR is a variable length

Like what:

char (10) type, if 1 ' a ' is stored, it is stored in this way

' A ', make up 10 characters, fill the left blank

Varchar (10) type, if 1 ' a ' is stored, it is stored in this way

' A ', without filling 10 characters, left without space

It looks like varchar saves space and char wastes space. Often using varchar, char, although a waste of space, but the storage efficiency is high, although varchar save space, but varchar will be redundant column deleted, more This step, reduce efficiency.

CHAR (11) is most suitable when we store the phone!

Char (n) where n is the maximum value of 255.

varchar (n) where n is the maximum value of 65535, however, in this 65,535 byte, there are two bytes to hold the information of the Varchar column itself. There are 65,533 remaining, and 1 bytes to hold the null value. There's 65532left.

In a simple sentence, the N maximum value in varchar (n) is 65532.

When a varchar or char represents a maximum byte that is already unable to meet the business requirements, for example, a kingdoms novel is stored in the database, is it possible for a varchar (max) char to solve it?

So there is this type: text, 2g is actually a kind of varchar, but the type of byte that can be stored in the range of 2g.

Tinytext Mediumtext Text Longtext

Enumeration type: Enumeration, say the end, you know the tail, meaning the value can be enumerated type.

For example: Week. Zodiac. Constellation.  Gender.  Degree. These are enumerated types.

Enumeration type is an enum in MySQL.

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Database Add Time Type