MySQL modify data type_ MySQL modify field type [easy to understand]

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mysql> alter table Table name modify column Field name type . data In the library address surface city The fields are varchar(30), Modify the type with ( Modify the type carefully , It may cause errors in the original data ).

mysql> alter table address modify column city char(30); You can modify the length with ( Modify the length , Ensure that it is not short of existing data , To ensure that the original data is not wrong )mysql> alter table address modify column city varchar(50);

alter table Table name modify column Field name type ;news Exterior and interior title Field The original length is 100 Characters , The current length should be changed to 130 Characters .

mysql Modify field type ：alter table news modify column title text; I found that using this sentence sql You can also directly modify the original type of the field !

It can usually be written as alter table Table name modify column Name The type of the new column, for example :student Columns in the table sname The type is char(20), Now change it to varchar(20),SQL The statement is as follows alter table student modify column sname varchar(20);

Method of modifying column name and column data type at the same time : It can usually be written as alter table Table name change column Old column names New column names New column type student Columns in the table sname The type is char(20), Now change it to stuname varchar(20)alter table student change column sname stuname varchar(20);

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