[Phpmyadmin-devel] Simulate UPDATE query

[Ashutosh Dhundhara]

Hi Marc,
I think if we will not use "<> 'NEW_VALUE'" in SELECT statement, then it will also return the rows which match the WHERE clause but already have the corresponding column's value = 'NEW_VALUE'. But the UPDATE statement won't count those rows in affected rows where there is already value = 'NEW_VALUE'.

Lets say:

`table_1`
+----+----------+
| id | value    |
+----+----------+
| 10 | value_10 |
| 20 | value_20 |
+----+----------+

UPDATE query: UPDATE table_1 SET value = 'value_10' WHERE id = 10;
Result:
Query OK, 0 rows affected (0.04 sec)
Rows matched: 1  Changed: 0  Warnings: 0

SELECT query: SELECT * FROM table_1 WHERE id = 10;
Result: 1 row in set.

But this query will yield same result:
SELECT * FROM table_1 WHERE id = 10 AND value <> 'value_10';

Result: Empty set (0.00 sec)

Please correct me if I am wrong.
 
Regards, 
Ashutosh Dhundhara


On Friday, 13 June 2014 10:42 PM, Marc Delisle <marc at infomarc.info> wrote:
 


Ashutosh Dhundhara a écrit :

> Hi,
> I was working on RFE #861 (Simulate UPDATE query).
> Lets say I have two tables:
> 
> `table_1`
> +----+----------+
> | id | value    |
> +----+----------+
> | 10 | value_10 |
> | 20 | value_20 |
> +----+----------+
> 
> `table_2`
> +----+----------+
> | id | value    |
> +----+----------+
> | 10 | value_10 |
> | 20 | value_20 |
> +----+----------+
> 
> UPDATE Query: UPDATE table_1, table_2 SET table_1.value = 'NEW_VALUE', table_2.value='NEW_VALUE' WHERE table_1.id > 10 AND table_2.id > 10;
> 
> This will affect 2 rows.
> 
> How to simulate this query using SELECT statement?
> 
> I was trying:
> 
> SELECT DISTINCT table_1.value, table_2.value FROM table_1, table_2 WHERE table_1.value <> 'NEW_VALUE' AND table_2.value <> 'NEW_VAUE' AND table_1.id > 10 AND table_2.id > 10;
> 
> 
> but this only returns 1 row.
> Can this be done in a single query only?
>  
> Regards, 
> Ashutosh Dhundhara

Hi Ashutosh,
any reason why in your SELECT statement, you are using "<> 'NEW_VALUE'" 
but in your UPDATE statement, you are using "='NEW_VALUE'" ?


-- 
Marc Delisle (phpMyAdmin)

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