Some times in SQL query you need to change the data type of table field with keeping the table structure as it is. Some thing like Integer to string, string to integer, string to date etc…. This type of data type conversion is known as data type casting. For this operation in SQL you can use mysql CAST function.
The CAST() function takes a value of one type and produce a value of another type.
What is Type Custing?
Converting an expression of a given type into another type is known as typecasting.

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If in a Database Table there are no index exist like primary or unique key then when you write a query for search anything from this table of course the search time cost will higher then when you use index in this table.

Cause in without index table the search perform must in entire table if in this table huge amount of record exist then you may find it is slow cause entire table searching.

Where if you use column index then searching cost will minimize from previous time cost. Cause when you use index it it will perform the search operation only on indexed row. Read more »