Get the id of a row when UNIQUE KEY is violated

Question

I have a table user. It has columns id and email.

USER TABLE

id | email
1  | xxx@gmail.com
2  | yyy@gmail.com


        

Answer 1

In scaning by UNIQUE KEY BTREE is used so it's quite fast.

Don't you want check for existing of value by yourself in additional select query

Answer 2

Use INSERT ... ON DUPLICATE KEY UPDATE, then get the autoincremented id as usual:

If a table contains an AUTO_INCREMENT column and INSERT ... ON DUPLICATE KEY UPDATE inserts or updates a row, the LAST_INSERT_ID() function returns the AUTO_INCREMENT value. Exception: For updates, LAST_INSERT_ID() is not meaningful prior to MySQL 5.1.12. However, you can work around this by using LAST_INSERT_ID(expr). Suppose that id is the AUTO_INCREMENT column. To make LAST_INSERT_ID() meaningful for updates, insert rows as follows:

INSERT INTO table (a,b,c) VALUES (1,2,3)
  ON DUPLICATE KEY UPDATE id=LAST_INSERT_ID(id), c=3;