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Sean Flanagan
33,235 PointsDELETE vs DROP vs TRUNCATE
Hi.
So have I got this right? DELETE deletes one table row, TRUNCATE deletes every row in a table, and DROP deletes the entire table?
Thanks in advance.
Sean
3 Answers
Steven Parker
231,261 PointsClose. You're right about TRUNCATE and DROP. Now DELETE can remove a single row, it can also delete every row. For example:
DELETE FROM mytable WHERE id = 21;
...would remove just one row (assuming id is a unique key and there is a row with 21 in it). But just this:
DELETE FROM mytable;
...would remove every row. By using different WHERE conditions you could also delete more than one, but not all rows.
Chung-Jun Wang
3,718 PointsMore details for these three keywords are:
DELETE will go into the table and delete row one by one, so if you have lots of rows like 1,000,000, it will take lots of time.
TRUNCATE will simply remove the table and re-create one empty table with same table name and same columns, so it will much faster if you want to remove all data from a big table and keep the empty table.
DROP will simply remove the table, so you will not have that table anymore.
Sam Donald
36,305 PointsSteven Parker don't you need to use the * to reference everything?
DELETE * FROM mytable;
Steven Parker
231,261 PointsThe * is used in a SELECT to represent all columns. But since DELETE works on rows, you don't need to specify columns.
Sean Flanagan
33,235 PointsSean Flanagan
33,235 PointsHi Steven.
DELETE comes across as flexible.
Thanks for the clarification. :-)
Sean