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Mysql – Removing all the rows in a table where a subset of columns have all 0s/NULL

I have a table with 30 columns. I want to remove all the rows in the table where a subset of columns have all the values in the row as either 0 or NULL. I know that I can write some query as

DELETE 
FROM Mytable
Where (col1 is NULL OR col1 = 0  ) AND
(col3 is NULL OR col1 = 0  ) AND
(col5 is NULL OR col1 = 0  )
.
.
.
many such lines.

Example Table (with smaller no of columns):

   |  col1 | col2   | col3  | col4  | col5   | col6 |
   |:---- |:------:| -----:||:---- |:------:| -----:|
R1 | 1    | 2      | 3     | 1     | 2      | 3     |
R2 | 1    |        | 0     |       | 0      |       |
R3 | 1    |        | 0     |       | 0      |       |
R4 | 1    | 2      | 3     | 1     | 2      | 3     |
R5 | 1    | 2      | 3     | 1     | 2      | 3     |

Let the subset of columns be {col2,col3,col4,col5,col6}.(This is just an example, there may be many such columns) . So the output of the query should be only the rows R1,R4 and R5 as R2,R3 contain either 0 or Null in the columns col2..6.

Output:

   |  col1 | col2   | col3  | col4  | col5   | col6  |
   |:---- |:------:| -----:||:---- |:------:| -----:|
R1 | 1    | 2      | 3     | 1     | 2      | 3     |
R4 | 1    | 2      | 3     | 1     | 2      | 3     |
R5 | 1    | 2      | 3     | 1     | 2      | 3     |

But I feel that the query I wrote isn’t a scalable way of writing this. Can anyone help me with this?

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2

Answers


  1. 0

    You could check if the sum of all the columns in question equals 0. The use of ifnull is to turn nulls into 0 to allow the arithmetic operation

    where ifnull(col1,0) + ifnull(col2,0) + ifnull(col3,0) .... = 0
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  2. 0

    I think you need to use a HAVING.

    The HAVING clause was added to SQL because the WHERE keyword cannot be used with aggregate functions.

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