Alter table 4

Question 1

ADD PRIMARY KEY and REMOVE PRIMARY KEY

Answer 1

ALTER TABLE tablename
ADD PRIMARY KEY (id);

ALTER TABLE tablename
DROP PRIMARY KEY;

Question 2

ADD FOREIGN KEY and REMOVE FOREIGN KEY

Answer 2

ALTER TABLE table_name
ADD CONSTRAINT constraint_name
FOREIGN KEY (column_name) REFERENCES table_name(column_name)

ALTER TABLE table_name
DROP FOREIGN KEY

Question 3

ADD UNIQUE CONSTRAINT and REMOVE

Answer 3

ALTER TABLE table_name
ADD CONSTRAINT constraintname UNIQUE (columnname)

ALTER TABLE tablename
DROP INDEX constraintname

Question 4

CHANGE COLUMN NAME

Answer 4

ALTER TABLE table_name CHANGE oldcolumnname newcolumnname DATA TYPE;
(και αντιστροφα).

Question 5

CHANGE COLUMN DATA TYPE

Answer 5

ALTER TABLE tablename

MODIFY columnname Data Type