When is the index used?

[lilleman]

Hi,

Let us assume that I create the following index on one of my tables.

CREATE INDEX added ON table ( date_field )

I know (at least I think I do ) that the index will be used when I execute the following query.

DELETE FROM table WHERE date_field = CURDATE()

My question is this. Will the index be used when I execute the following query?

DELETE FROM table WHERE date_field < DATE_SUB(CURDATE(), INTERVAL 14 DAY)

Yours, Erik.

[r937]

i think yes

because the expression on the right side of the operator will resolve to a specific value that is the same datatype as the column on the left side

[lilleman]

Hi,

Alright. Thanks for the explanation!

Yours, Erik.

[dotJoon]

table1

(table1_ID) table1_say
(1) France
(2) America
(3) Japan

table2

(table2_ID) table2_say
(2) New Yok
(1) Paris
(2) Chicago
(3) Tokyo

I have the data above in myTables.

Table1_ID is primary.
Table2_ID is a foreign key connected to table1_ID


Should table2_ID be indexed?

Thanks in Advance