What is casting in SQL?

Parthiban Kannan

Updated on January 8, 2026

< 1 min read

Casting in SQL is converting a value from one data type to another.
It is done using functions like CAST() or CONVERT().
In my project, we cast varchar order IDs to int for joining tables.
Casting ensures operations like comparisons and calculations work correctly.
It helps align incompatible data types during extraction or reporting.
Without casting, queries may fail or return incorrect results.
It is commonly used in joins, filters, and data transformations.