CODEWITHSUNDEEP
mysqlsqlindexingalter-tableunique-index
D_R
D_R

Reputation: 4972

2 columns unique in mysql table

Is it possible to make a 2 coulmns unique in mysql db? for example:

ID | columnA | columnB
 1 | Dan     | 1
 2 | Dan     | 2
 3 | Zak     | 1
 4 | Dan     | 1 (WHEN TRYING TO INSERT ROW 4 - NOT ALLOWED! DUPLICATE COULMNA + COLUMNB)

Upvotes: 1

Views: 74

Answers (2)

Nagaraj S
Nagaraj S

Reputation: 13484

A unique index guarantees that the index key contains no duplicate values and therefore every row in the table is in some way unique. There are no significant differences between creating a UNIQUE constraint and creating a unique index that is independent of a constraint. Data validation occurs in the same manner, and the query optimizer does not differentiate between a unique index created by a constraint or manually created. However, creating a UNIQUE constraint on the column makes the objective of the index clear

link

Upvotes: 0

Saharsh Shah
Saharsh Shah

Reputation: 29071

Try this: 

ALTER TABLE tableA ADD UNIQUE INDEX idxColAB (columnA, columnB)

Upvotes: 6

Related Questions