How to convert a value of one type to another type in SQL server

Convert means to change the form or value of something. The CONVERT() function in SQL server is used to convert a value of one type to another type.

Syntax :

SELECT CONVERT 
( target_type ( length ), expression ) 

Parameters used :

• target_type –
  It is the target data type to which the to expression will be converted, e.g: INT, BIT, SQL_VARIANT, etc.
• length –
  It provides the length of the target_type. Length is not mandatory. Default length is set to 30.
• expression –
  expression is anything that will be converted.

Example-1 :
To convert a decimal to an integer :
In below example, the CONVERT() function is used to convert the decimal number 7.85 to an integer.

SELECT CONVERT(INT, 7.85) AS Result;

Output :

Result
7

Example-2 :
To convert a decimal to another decimal :
In below example, the CONVERT() function is used to convert the decimal number 8.99 to another decimal number with zero scales.

SELECT CAST(8.99 AS DEC(2, 0)) 
AS Result;

Output :

Result
9

Example-3 :
To convert a string to a datetime value :
In below example, the CONVERT() function is used to convert the string ‘2020-05-14’ to a datetime value.

SELECT CONVERT(DATETIME, '2020-05-14') 
AS Result;

Output :

Result
2019-03-14 00:00:00.000

Example-4 :
To convert a datetime value to a string :
In below example, the CONVERT() function is used to convert the current date and time to a string with a definite style.

SELECT  CONVERT(VARCHAR, GETDATE(), 13) 
AS Result;

Output :

Result
05 Sep 2020 16:59:01:380