Mayou Mayou - 5 months ago 19
SQL Question

Replace empty cells with NULL values in large number of columns

I have SQL table that has a large number of columns. For some reason, some columns have empty cells instead of NULL cells. I would like to make all empty cells in all the columns to be NULL.

I know that the way to go for a single column is:

UPDATE your_table SET column = NULL WHERE column = ''


However, I am not sure how to execute a similar logic efficiently for all columns without having to write the column names one by one.

Thanks,

Answer

Run the following query:

SELECT 'UPDATE yourtable SET ' + name + ' = NULL WHERE ' + name + ' = '''';'
FROM syscolumns
WHERE id = object_id('yourtable')
  AND isnullable = 1;

The output of this query will be a chunk of SQL script like this:

UPDATE yourtable SET column1 = NULL WHERE column1 = '';
UPDATE yourtable SET column2 = NULL WHERE column2 = '';
UPDATE yourtable SET column3 = NULL WHERE column3 = '';
-- etc...

Copy and paste that SQL script into a new query and run it to update all your columns.

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