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They can contain characters normally not supported in SQL identifiers, and they can be identical to a reserved word, e.g. a column named YEAR is specified as "YEAR". In MySQL, double quotes are string literal delimiters by default instead. Enabling the ansi_quotes SQL mode enforces the SQL standard behavior.
Single quotes, double quotes, backslashes and null characters in all user-supplied data all have a backslash prepended to them before being passed to the script in the $_GET, $_REQUEST, $_POST and $_COOKIE global variables. Developers can then in theory use string concatenation to construct safe SQL queries with data provided by the user.
Furthermore, (unlike in the literature example), the third-level nested quote must be escaped in order not to conflict with either the first- or second-level quote delimiters. This is true regardless of alternating-symbol encapsulation. Every level after the third level must be recursively escaped for all the levels of quotes in which it is ...
Using a database-specific stored procedure that generates the surrogate key, performs the INSERT operation, and finally returns the generated key. For example, in Microsoft SQL Server, the key is retrieved via the SCOPE_IDENTITY() special function, while in SQLite the function is named last_insert_rowid().
The standard specifies enclosing reserved words in double quotes, but in practice the exact mechanism varies by implementation; MySQL, for example, allows reserved words to be used in other contexts by enclosing them in backticks, and Microsoft SQL Server uses square brackets.
One of the oldest examples is in shell scripts, where single quotes indicate a raw string or "literal string", while double quotes have escape sequences and variable interpolation. For example, in Python , raw strings are preceded by an r or R – compare 'C:\\Windows' with r'C:\Windows' (though, a Python raw string cannot end in an odd number ...
Double quotes are not officially named in Lojban, but sometimes called lubu, following the same pattern as vowel letters, e.g. a = abu: Lojban uses the words lu and li’u, rather than punctuation, to surround quotes of grammatically correct Lojban. [49] Double quotes can also be used for aesthetic purposes.
String interpolation, like string concatenation, may lead to security problems. If user input data is improperly escaped or filtered, the system will be exposed to SQL injection, script injection, XML external entity (XXE) injection, and cross-site scripting (XSS) attacks. [4] An SQL injection example: query = "SELECT x, y, z FROM Table WHERE ...