How to Select Rows Having Column Value as Null

How to select rows having column value as null?

In both Postgres and SQL server,

SELECT * FROM tab WHERE is_visible is null;

If you want to select the rows for which column values are not null, then use is not null operator:

SELECT * FROM tab WHERE is_visible is not null;

Selecting Rows with one column or Columns with NULL value when even one have value

You could use either the GREATEST or LEAST function here:

SELECT *
FROM yourTable
WHERE GREATEST(col1, col2, col3, col4) IS NULL;

The above call to GREATEST would only be NULL if at least one of the four columns have a NULL value.

If you want to also ensure that a given row has at least one non NULL value, then add a condition for that to the WHERE clause:

SELECT *
FROM yourTable
WHERE
    GREATEST(col1, col2, col3, col4) IS NULL AND
    COALESCE(col1, col2, col3, col4) IS NOT NULL;

how to select rows with no null values (in any column) in SQL?

You need to explicitly list each column. I would recommend:

select t.*
from t
where col1 is not null and col2 is not null and . . . 

Some people might prefer a more concise (but slower) method such as:

where concat(col1, col2, col3, . . . ) is not null

This is not actually a simple way to express this, although you can construct the query using metadata table or a spreadsheet.

How to select rows with NaN in particular column?

Try the following:

df[df['Col2'].isnull()]

MySQL - Selecting rows with null columns

the best answer that does not need to hard-code the column names is:

DECLARE @sqlStr VARCHAR(max) = (
        SELECT stuff((
                    SELECT 'and ' + c.NAME + ' is null '
                    FROM sys.columns c
                    WHERE object_name(object_id) = 'yourtablename'
                    ORDER BY c.NAME
                    FOR XML PATH('')
                    ), 1, 3, '')
        )

SET @sqlStr = 'select * from ' + yourtablename + ' where ' + @sqlStr

PRINT @sqlStr

EXEC (@sqlStr)

Select rows where column is null

Do you mean something like:

SELECT COLUMN1, COLUMN2 FROM MY_TABLE WHERE COLUMN1 = 'Value' OR COLUMN1 IS NULL

?

Query to find null of specific column with multiple entries

Use NOT EXISTS:

SELECT DISTINCT u1.userid
FROM User u1
WHERE NOT EXISTS (SELECT 1 FROM User u2 WHERE u2.userid = u1.userid AND u2.col2 IS NOT NULL)

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