How to Cast Data Types from Varchar to Int in PostgreSQL SELECT Statement?

Casting Data Types in Postgres

Question: How can I cast a column's data type from varchar to int in a Postgres SELECT statement?

Answer:

Postgres offers several options for casting data types:

• cast(varchar_col AS int): SQL standard syntax
• varchar_col::int: Postgres syntax shorthand

Both variants are generally interchangeable, but the second may require additional parentheses in certain scenarios.

Additionally, you can use these syntax variations:

• int4(varchar_col): Only works for specific type names (e.g., int4)
• int '123': Must use an untyped, quoted string literal

Note that the varchar_col must contain only numerals and an optional leading sign. Leading or trailing whitespace is ignored.

Example:

<code class="sql">SELECT cast(passenger_name AS int), age FROM passengers;</code>

This query will cast the passenger_name column, which is a varchar, to an int before returning the result.

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