Is SQL syntax case sensitive?
The SQL keywords are case insensitive (SELECT, FROM, WHERE, etc), but they are often written in all caps. However, in some setups, table and column names are case sensitive.
MySQL has a configuration option to enable/disable it. Usually case sensitive table and column names are the default on Linux MySQL and case insensitive used to be the default on Windows, but now the installer asked about this during setup. For SQL Server it is a function of the database's collation setting.
Here is the MySQL page about name case-sensitivity
Here is the article in MSDN about collations for SQL Server
The SQL-92 specification states that identifiers might be quoted, or unquoted. If both sides are unquoted then they are always case insensitive, e.g., table_name == TAble_nAmE.
However, quoted identifiers are case sensitive, e.g., "table_name" != "TAble_naME". Also based on the specification if you wish to compare unquoted identifiers with quoted ones, then unquoted and quoted identifiers can be considered the same, if the unquoted characters are uppercased, e.g. TABLE_NAME == "TABLE_NAME", but TABLE_NAME != "table_name" or TABLE_NAME != "TAble_NaMe".
Here is the relevant part of the specification (section 5.2.13):
- A <regular identifier> and a <delimited identifier> are equivalent if the <identifier body> of the <regular identifier> (with every letter that is a lower-case letter replaced by the equivalent upper-case letter or letters) and the <delimited identifier body> of the <delimited identifier> (with all occurrences of <quote> replaced by <quote symbol> and all occurrences of <doublequote symbol> replaced by <double quote>), considered as the repetition of a <character string literal> that specifies a <character set specification> of SQL_TEXT and an implementation- defined collation that is sensitive to case, compare equally according to the comparison rules in Subclause 8.2, "<comparison predicate>".
Note, that just like with other parts of the SQL standard, not all databases follow this section fully. PostgreSQL for example stores all unquoted identifiers lowercased instead of uppercased, so table_name == "table_name" (which is exactly the opposite of the standard). Also some databases are case insensitive all the time, or case-sensitiveness depend on some setting in the DB or are dependent on some of the properties of the system, usually whether the file system is case sensitive or not.
Note that some database tools might send identifiers quoted all the time, so in instances where you mix queries generated by some tool (like a CREATE TABLE query generated by Liquibase or other DB migration tool), with hand made queries (like a simple JDBC select in your application) you have to make sure that the cases are consistent, especially on databases where quoted and unquoted identifiers are different (DB2, PostgreSQL, etc.)
This isn't strictly SQL language, but in SQL Server if your database collation is case-sensitive, then all table names are case-sensitive.