How to Safely Insert Text with Single Quotes into a PostgreSQL Database?

Safely insert text containing single quotes into a PostgreSQL database

Inserting text containing single quotes into a PostgreSQL database table can be tricky, and trying to do so directly may result in errors. To handle this effectively, be sure to use an escaping mechanism to ensure that the database interprets single quotes correctly.

Single quote string injection problem:

<code class="language-sql">insert into test values (1,'user's log');</code>

Here, an error occurs due to unbalanced single quotes in the string. To fix this, you can escape the single quotes by doubling them, like this:

<code class="language-sql">insert into test values (1,'user''s log');</code>

Escape single quotes:

This method is commonly used to escape single quotes in PostgreSQL. By doubling the quotes, you tell the database that they should be treated as part of the string, not as delimiters. Alternatively, you can use the backslash character to escape single quotes:

<code class="language-sql">insert into test values (1,E'user\'s log');</code>

Dollar quote string:

If you're dealing with multiple levels of escaping or complex strings, dollar-quoted strings provide a cleaner, more readable solution. To quote a string with dollar signs, enclose the string with dollar signs ($):

<code class="language-sql">insert into test values (1,$'user's log'$);</code>

Functions for escaping values:

PostgreSQL also provides functions specifically for escaping values. These functions include:

• quote_literal(): Escape a string to be used in a query.
• quote_nullable(): Escapes a string to handle empty input by outputting NULL as an unquoted string.

Example:

<code class="language-sql">insert into test values (1,quote_literal('user's log'));</code>

Use SQL escape mechanism:

Yes, it is possible to insert text containing single quotes into PostgreSQL using the SQL escape mechanism. The methods described above, such as doubling single quotes or quoting strings with dollar signs, are considered valid SQL escape mechanisms.

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