How to Properly Use Single Quotes, Double Quotes, and Backticks in MySQL Queries?

Best practices for single quotes, double quotes and backticks in MySQL

When writing MySQL queries, proper use of quoting conventions is critical to ensuring data integrity and consistency. Here's a complete guide on how and when to use single quotes, double quotes, and backticks:

Backticks (`)

• Use backticks when table and column identifiers meet the following conditions:

  • is a MySQL reserved keyword
  • Contains space characters or characters outside the ASCII character set

• It is recommended to avoid using reserved keywords as identifiers to prevent quoting issues.

Single quote (')

• In VALUES() lists, use single quotes for string values.
• Use single quotes for DATE and DATETIME literals.

Double quotes (")

• Double quotes are also supported for string values, but for compatibility with other RDBMS, single quotes are preferred.

Example:

$query = "INSERT INTO `table` (`id`, `col1`, `col2`, `date`, `updated`) 
                       VALUES (NULL, 'val1', 'val2', '2001-01-01', NOW())";

Variable interpolation

• When interpolating variables, use double quotes for PHP strings and single quotes for variables in the VALUES list.
• Escape variables before interpolation to prevent SQL injection.

Prepared statements

• Consult the documentation for your chosen API to determine whether placeholders require quotes.
• Most APIs (such as PDO and MySQLi) expect unquoted placeholders.

Characters that require backtick quoting

Table and column identifiers must be quoted if they contain characters outside the following character sets:

• ASCII: [0-9,a-z,A-Z$_]

Summary:

Understanding the correct use of single quotes, double quotes, and backticks in MySQL is critical to writing accurate and consistent queries. By following these best practices, you can ensure the integrity of your data and the efficiency of your database operations.

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