ALTER command can be used to add/modify definition of various aspects of database and its objects.<br>
SYNTAX
Dropping, Adding or Repositioning a Column<br>
--drop existing column
alter table test_tbl drop i;
--add the same column at the end of the table
alter table test_tbl add i int;
--drop existing column
alter table test_tbl drop i;
--add the same column at top of the able
alter table test_tbl add i int first;
--drop existing column
alter table test_tbl drop i;
--add same column at after column c
alter table test_tbl add i int after c;
Changing a Column Definition or a Name<br>
--change datatype
alter table test_tbl modify col1 char(10);
--change column name
alter table test_tbl change col1 col1new bigint;
--change datatype
alter table test_tbl change col1new col1new int(1);
--setting the default value
alter table test_tbl modify i bigint not null default 100;
Changing a Column's Default Value<br>
--setting a default value of a column
alter table test_tbl i set default 1000;
--remove the default value of a column
alter table test_tbl alter i drop default;
Changing a Table Type<br>
--change the db engine type for a given table
alter table test_tbl type = myisam;
Renaming a Table<br>
--rename a table
alter table test_tbl rename to alter_tbl;
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