How Do I Cast a VARCHAR to an INTEGER in PostgreSQL?

PostgreSQL data type conversion: Convert VARCHAR to INTEGER

In PostgreSQL SQL, you can convert one data type to another directly in the SELECT statement. To convert a varchar column to an integer, there are several ways:

1. Standard SQL syntax:

<code class="language-sql">cast(varchar_col AS int)</code>

2. PostgreSQL shorthand syntax:

<code class="language-sql">varchar_col::int</code>

These syntaxes can be used in a variety of contexts. However, in some cases, additional bracket nesting or function notation may be required.

3. Named type conversion:

<code class="language-sql">int4(varchar_col)</code>

This format uses internal type names and is limited to certain data types.

4. Untyped string literal:

<code class="language-sql">int '123'</code>

This method requires an untyped quoted string literal.

It is important to note that when converting to an integer, the string must conform to the following format: an optional leading symbol followed by a number. Whitespace around the string will be ignored.

Detailed documentation on conversions is available in the PostgreSQL manual.

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