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Ho to do this? What query can be written by using select statement where all nulls should be replaced with 123?
I know we can do this y using, update tablename set fieldname = "123" where fieldname is null;
but can't do it using select statement.
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The ISNULL Function is a built-in function to replace nulls with specified replacement values. To use this function, all you need to do is pass the column name in the first parameter and in the second parameter pass the value with which you want to replace the null value.
Use IFNULL or COALESCE() function in order to convert MySQL NULL to 0. Insert some records in the table using insert command. Display all records from the table using select statement.
Null Values can be replaced in SQL by using UPDATE, SET, and WHERE to search a column in a table for nulls and replace them.
We can replace NULL values with a specific value using the SQL Server ISNULL Function. The syntax for the SQL ISNULL function is as follow. The SQL Server ISNULL function returns the replacement value if the first parameter expression evaluates to NULL.
You have a lot of options for substituting NULL values in MySQL:
CASE
select case
when fieldname is null then '123'
else fieldname end as fieldname
from tablename
COALESCE
select coalesce(fieldname, '123') as fieldname
from tablename
IFNULL
select ifnull(fieldname, '123') as fieldname
from tablename
There is a statement called IFNULL, which takes all the input values and returns the first non NULL value.
example:
select IFNULL(column, 1) FROM table;
http://dev.mysql.com/doc/refman/5.0/en/control-flow-functions.html#function_ifnull
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