Question

I have many columns in a table which needs to be checked against some value and values needs to be replaced if match found..

So basically I am looking for a query which takes column name as sort of variable and loops through the table and updates the column value if matched..

I could do that with php, having as many queries as columns.. but that’s what I don’t want..

p.s. I know its a bad design, and in normal case such requirements never occur, but sadly it is what it is..

Answer 1

In many statements:

UPDATE tableX 
SET   col_1 = 'newvalue' 
WHERE col_1 = 'ram';

UPDATE tableX 
SET   col_2 = 'newvalue' 
WHERE col_2 = 'ram';

...

UPDATE tableX 
SET   col_N = 'newvalue' 
WHERE col_N = 'ram';

---

In one statement

UPDATE tableX 
SET   col_1 = CASE WHEN col_1 = 'ram'
                     THEN 'newvalue' 
                     ELSE col_1 
              END
    , col_2 = CASE WHEN col_2 = 'ram'
                     THEN 'newvalue' 
                     ELSE col_2 
              END
    ...

    , col_N = CASE WHEN col_N = 'ram'
                     THEN 'newvalue' 
                     ELSE col_N 
              END
 ;

---

You can write the statements by hand or with dynamic SQL (if the columns and tables to work are too many).