Shulou(Shulou.com)05/31 Report--

Mysql about the table operation is how, many novices are not very clear about this, in order to help you solve this problem, the following editor will explain in detail for you, people with this need can come to learn, I hope you can gain something.

Create a database

Createdatabase database name

Switch database

Use database name

Build a table:

Createtable table name (

Field name 1, type, constraint

Field name 2, type, constraint

...

)

Constraints:

1. Primary key constraint

1) add primarykey to the field type directly when creating the table

2) add the constraint constraint name primarykey (field name) at the end of the table

3) modify altertable table name addconstraint constraint name primarykey (field name) outside the table

two。 Check constraint

1) add check (constraint) directly after the table type is created

2) add the constraint constraint name check (constraint condition) at the end of the table

3) modify the altertable table name outside the table addconstraint constraint name check (constraint condition)

Note: mysql does not support checking constraints, but writing check constraints will not report an error

3. Non-empty constraint

1) add notnull directly after creating the type of the table

2) add the constraint constraint name check (field name isnotnull) at the end of the table

3) modify the altertable table name modify field name field type notnull outside the table

4. Unique constraint

1) add unique directly after creating the type of the table

2) add the constraint constraint name unqiue (field name) at the end of the table

3) modify the altertable table name addconstraint constraint name unique (field name) outside the table

5. Foreign key constraint

1) add the references parent table name (parent table primary key name) directly after creating the table type

2) add the constraint constraint name foreignkey (field name) references parent table name (parent table primary key name) at the end of the table

3) modify altertable table name addconstraint constraint name foreignkey (field name) references parent table name (parent table primary key name) ondeletesetnullonupdatacascade outside the table

6. Default constraint

1) add the default default value directly after creating the type of the table

2) modify the altertable table name addconstraint constraint name outside the table

Delete constraint

Altertable table name dropconstraint constraint name

Modification of table

1) add a field

Altertable table name add field name field type Note: when there is already a value in the table, you cannot add a non-null constraint

2) Delete a field

Altertable table name drop field name

3) modify the field type

Altertable table name modify field name new field type

4) modify the field name

Altertable table name change field name new field name field type

5) modify the table name

Altertable table name renameas new table name

6) delete the table

Droptable table name

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