MySQL Data modification

1 Adding a single column

A ALTER TABLE list name add the parameter name ( such as age) to add the content ( such as 21); "At the bottom of all columns"

b ALTER table list name add the parameter name ( such as age) to add the content ( such as Tirst); "The newly added column is at the front"

C ALTER table list name add the parameter name (for example, age ) to add to the column specified by Afier (for example) ; " The newly added column is located below the column you specified.

2 adding multiple columns

altertableList nameADDthe name of the parameter to add(such as age) content(as);the name of the parameter to add(such as name)  content(such as Sulinlin);wait"At the bottom of all columns"

3 Deleting a single column

alteertable List name DROP the name of the parameter to delete ( e.g. age ) ;

4 Deleting multiple columns

ALTER table name drop the parameter name ( such as name ) to delete , and also the parameter name ( such as age ) to delete; wait

5 You can also delete edges to add

6 Adding a PRIMARY KEY constraint ( only one )

ALTER TABLE list name PRIMARY REY ( the primary KEY constraint name to be added );( is actually the name of the parameter name)

7 Adding a unique constraint ( can have multiple )

ALTER TABLE list name add unique ( the unique constraint name to add );( is actually the parameter name, such as age )

8 adding foreign KEY constraints

altertable List name ADD FOREIGN Key ( foreign key parameter ) refrences List name (name of the parameter);

9 Adding a DEFAULT constraint

Alter ABLE table name alter parameter SET default value ;

10 Deleting a DEFAULT constraint

ALTER TABLE name alter parameter DROP DEFAULT;

11 See which parameters in the list are constrained and indexed

First step SHOW INDEXES from list name;

The second step SHOW INDEXES from list name \g;

12 Deleting a PRIMARY KEY constraint

ALTER table name DROP primapy KEY;

13 Deleting a UNIQUE constraint

ALTER table name DROP INDEX parameter;

14 Deleting a FOREIGN KEY constraint

ALTER table name DROP FOREIGN key foreign KEY constraint name;

15 Viewing FOREIGN KEY constraint names

SHOW CREATE table table name;

16 Deleting an index

ALTER TABCE table name DROP Index has an indexed parameter name;

MySQL Data modification