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24-01-2024
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DDL
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Alter statement:
alter statement is used for the modify structre of existing table;
alter statement is used for add,rename,modify,drop in an existing tables.


1.change table name
syntax:- alter table table_name rename to new_tablename;
ex:-alter table student rename to studentinfo;

2. change column name of existing table
syntax:  alter table table_name rename column oldcolname to newcolname;
ex: alter table studentinfo rename column address to addrs;

3. add new column in existing table.
syntax:-alter table table_name add column newcolumn_name datatype;
exa;- alter table studentinfo add column lname varchar(50);

4.modify datatype of existing column in the  tables;
syntax:alter table tablename modify column colname newdatatype;
exa:-alter table studentinfo modify column gender varchar(10);

5.delete column from existing table
syntax :-alter table tablename drop column colname;
exa: alter table studentinfo drop column lname;
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