What is the purpose of the SQL CAST function?

The CAST function in SQL is used to convert the data type of an expression or column to another data type. It can be used in queries to handle conversions between different data types, such as converting numbers to strings, dates to strings, or strings to numbers.

Grammar: the rules of a language that govern how words and sentences are constructed.

CAST(expression AS data_type)

In this case, ‘expression’ refers to the expression or column to be converted, and ‘data_type’ refers to the data type it should be converted to.

For instance, if there is a column containing numbers but it needs to be displayed as a string in the query results, you can use the CAST function to convert it as shown below:

SELECT CAST(column_name AS varchar) FROM table_name

Strings can also be converted into numbers, as shown below:

SELECT CAST('123' AS int)

This will convert the string ‘123’ into an integer type.