SQL statements can include programming elements just like most other programming languages. (You may want to see my section on Programming.)
Developer Comments. Started by two dashes
--or enclosed by slash-asterisk
*/. MySQL uses
--(note the following space),
#(the latter is just like
Statement Layout. Some specific to SQL-Transact.
Expressions. In SQL, an expression evaluates a single data value for each row in the result set. EG:
SELECT ID, 1+2, price*2 FROM TableA. In most programming languages, expressions are symbols and operators that evaluate to a single data value. Expressions can include constants, functions that return one value, column references, or variables.
- Expressions. In SQL, an expression evaluates a single data value for each row in the result set. EG:
- Data Types. Each column, local variable, expression, and parameter has a related data type.
- Identifiers. Labels for database objects.
Operators. Here is the precedence list in SQL Server:
- Unary operators: + (Positive), - (Negative), ~ (Bitwise NOT)
Math and string operators:
- * (Multiply), / (Division), % (Modulo)
- + (Add), (+ Concatenate), - (Subtract)
- Comparison operators: =, >, <, >=, <=, <>, !=, !>, !<
- Bitwise operators: ^ (Bitwise XOR), & (Bitwise AND), | (Bitwise OR)
- ALL, ANY, BETWEEN, EXISTS, IN, LIKE, OR, SOME
- Assignment operator: =
- Flow Control
- Program Halts
- Reserved Keywords. Certain keywords are reserved by SQL Server because they have particular use in T-SQL syntax.
There are four ways that multiple statements can be executed:
Batches are non-compiled multiple statements sent to the server. (The end of a batch is signaled in SQL Server Query Analyzer, osql, and isql by use of the
- Scripts are statements stored as files. Scripts usually consist of batches.
- Stored Procedures are pre-compiled statements on the server that can be called upon.
- Triggers are stored procedures that are not called but execute when certain events occur.