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Elements of SQL Statements

SQL Operators

An operatoris a symbol that represents an action performed on one or more expressions.

There are three types of SQL operators:

  • Arithmetic

  • Comparison

  • Logical

Arithmetic Operators

Arithmetic operators are used to combine numeric expressions arithmetically to form other numeric expressions.

The arithmetic operators (in order of precedence) are as follows:

Arithmetic Operator Description
+ and - Positive, negative (unary)
** Exponentiation (binary)
* and / Multiplication, division (binary)
+ and - Addition, subtraction (binary)

Unary operators group from right to left, while binary operators group from left to right. Use the unary negative (-) to reverse the algebraic sign of a value.

To force a desired order of evaluation, use parentheses. For example:

(job.lowsal + 1000) * 12

is an expression in which the parentheses force the addition operator (+) to take precedence over the multiplication operator (*).

Comparison Operators

Comparison operators compare two expressions. SQL includes the following comparison operators:

Comparison Operator Description
= Equal to
<> Not equal to
> Greater than
>= Greater than or equal to
< Less than
<= Less than or equal to
IS NOT DISTINCT FROM Equal to, treating NULLs as equal
IS DISTINCT FROM No equal to, treating NULLs as equal

The <> operator can also be specified as != or ^=.

All comparison operators are of equal precedence.

The equal sign (=) also serves as the assignment operator in assignment operations.

More information:

Comparison Predicate

Logical Operators

SQL has three logical operators, shown in order of precedence:

  • NOT

  • AND

  • OR

Use parentheses to change the order of evaluation. For example, the following expression:

exprA OR exprB AND exprC

is evaluated as:

exprA OR (exprB AND exprC)

When parentheses are used as follows:

(exprA OR exprB) AND exprC

Actian Data Platform evaluates (exprA OR exprB) first, then uses the AND operator*for*the result with exprC.

Parentheses can also be used to change the default evaluation order of a series of expressions combined with the same logical operator. For example, the following expression:

exprA AND exprB AND exprC

is evaluated as:

(exprA AND exprB) AND exprC

To change this default left-to-right grouping, use parentheses as follows:

exprA AND (exprB AND exprC)

The parentheses direct the Actian Data Platform to use the AND operator for**exprB and exprC, then use the AND operator for that result with exprA.