mysql string to date conversion - mysql

Question

Need help to suggest sql query where I have a varchar column called Timing like below
+---------------------+
| Timing | MO |
+---------------------+
|7/11/2016 20:45 |ABC |
|7/12/2016 20:45 |ABC |
|2016-07-11 00:00|ABC |
|2016-07-12 00:00|ABC |
+---------------------+
I need to extract date from the Timing column but tricky part is the date is not always in same format. I need to output timing column as below
+-------------+
| Timing | MO|
+-------------+
|7/11/2016|ABC|
|7/12/2016|ABC|
|7/11/2016|ABC|
|7/12/2016|ABC|
+-------------+

Answer 1

It's simple enough using substring and replace functions to cast varchar as data and recast them to you required output.
for example
DROP TABLE T;
CREATE TABLE T (TIMING VARCHAR(20),MO VARCHAR(2));
INSERT INTO T VALUES
('7/11/2016 20:45' ,'AB'),
('7/12/2016 20:45' ,'AB'),
('2016-07-11 00:00','AB'),
('2016-07-12 00:00','AB'),
('27/06/2016 20:45' ,'AB'),
('29/05/2016 20:45' ,'AB')
*/
SELECT *,
CASE
WHEN INSTR(TIMING,'/') = 0 THEN
CASE WHEN INSTR(TIMING,'-') = 5 THEN CAST(TIMING AS DATE)
end
WHEN INSTR(TIMING,'/') = 3 THEN
CAST(
CONCAT(
SUBSTRING(CONCAT('0',TIMING),8,4)
,'-'
,SUBSTRING(CONCAT('0',TIMING),5,2)
,'-'
,SUBSTRING(CONCAT('0',TIMING),1,2)
)
AS DATE
)
WHEN INSTR(TIMING,'/') = 2 THEN
CAST(
CONCAT(
SUBSTRING(CONCAT('0',TIMING),7,4)
,'-'
,SUBSTRING(CONCAT('0',TIMING),4,2)
,'-'
,SUBSTRING(CONCAT('0',TIMING),1,2)
)
AS DATE
)
END
FROM T
results in
-----------------------------------------------------------------------------+
| 7/11/2016 20:45 | AB | 2016-11-07 |
| 7/12/2016 20:45 | AB | 2016-12-07 |
| 2016-07-11 00:00 | AB | 2016-07-11 |
| 2016-07-12 00:00 | AB | 2016-07-12 |
| 27/06/2016 20:45 | AB | 2016-06-02 |
| 29/05/2016 20:45 | AB | 2016-05-02 |
+------------------+------+-----------------------------------------------------
You do have to code for every known variant - in this case I have identified that 7/11/2016 needs to left padded with zero and slashes replaced with dashs before date conversion. Hopefully you have a limited number of date variations in your source to code for and you will end up with a large query - but that's life. God luck,