Database common operations Records: New Add column, rename column, modify column length and type, delete column, rename table name, etc.

1. Add a new column to the existing table in the database

Statement:altertable    name  add   column name   type    Example:alter  MyUser  ADD  Userdesc  VARCHAR(+);

2. Name the rename in the existing tables in the database

Statement:altertablecolumn to    new columns name;   Example:altertablecolumn to Pk_group;

3. Modify the length and type of columns in the tables that are already in the database

Statement:alter table   name modify  column name  type (length);   Example:altertable myuser  Modify  Varchar(+);        Alter Table SMALLINT;

4. Delete a column for existing tables in the database

Statement:altertable  drop  column name, example:altertable  Dropcolumn Venterplan;

5. Renaming existing tables in the database

 table name to    new show;    Table  to user;

6. Add more columns for existing tables in the database

Statement:altertableadd (column name type, column name type,...) ; Example: Alter Table Add VARCHAR (255varchar(+));

7. Copy table data for existing tables in the database

Statement:Insert into Aa_files (id,name,diskSelect id,name,disk, Hash,size, Date,'yy' from Yy_files;

Database common operations Records: New Add column, rename column, modify column length and type, delete column, rename table name, etc.