Mysql training for BE IT students Bangalore
« on: November 10, 2011, 01:04:04 PM »


SQL NULL Values
There is a optional column in a table, then we can insert a new record or update an existing record without adding a value to that null value column. This means that the  particular  field will have the  NULL value.
NULL values are different from the  other values when it is compared.
NULL is used as a placeholder for unknown or inapplicable values.
Compare NULL and 0; they are not equivalent.
Example:
Selecting NULL value column
SELECT name,billno,pay  FROM client WHERE pay IS NULL
Selecting NULL value column
SELECT name,billno,pay  FROM client WHERE pay IS NOT NULL

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