PostgreSQL - Operators


Advertisements


What is an Operator in PostgreSQL?

An operator is a reserved word or a character used primarily in a PostgreSQL statement's WHERE clause to perform operation(s), such as comparisons and arithmetic operations.

Operators are used to specify conditions in a PostgreSQL statement and to serve as conjunctions for multiple conditions in a statement.

  • Arithmetic operators
  • Comparison operators
  • Logical operators
  • Bitwise operators

PostgreSQL Arithmetic Operators

Assume variable a holds 2 and variable b holds 3, then −

Example

Operator Description Example
+ Addition - Adds values on either side of the operator a + b will give 5
- Subtraction - Subtracts right hand operand from left hand operand a - b will give -1
* Multiplication - Multiplies values on either side of the operator a * b will give 6
/ Division - Divides left hand operand by right hand operand b / a will give 1
% Modulus - Divides left hand operand by right hand operand and returns remainder b % a will give 1
^ Exponentiation - This gives the exponent value of the right hand operand a ^ b will give 8
|/ square root |/ 25.0 will give 5
||/ Cube root ||/ 27.0 will give 3
! factorial 5 ! will give 120
!! factorial (prefix operator) !! 5 will give 120

PostgreSQL Comparison Operators

Assume variable a holds 10 and variable b holds 20, then −

Show Examples

Operator Description Example
= Checks if the values of two operands are equal or not, if yes then condition becomes true. (a = b) is not true.
!= Checks if the values of two operands are equal or not, if values are not equal then condition becomes true. (a != b) is true.
<> Checks if the values of two operands are equal or not, if values are not equal then condition becomes true. (a <> b) is true.
> Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true. (a > b) is not true.
< Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true. (a < b) is true.
>= Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true. (a >= b) is not true.
<= Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true. (a <= b) is true.

PostgreSQL Logical Operators

Here is a list of all the logical operators available in PostgresSQL.

Show Examples

S. No. Operator & Description
1

AND

The AND operator allows the existence of multiple conditions in a PostgresSQL statement's WHERE clause.

2

NOT

The NOT operator reverses the meaning of the logical operator with which it is used. Eg. NOT EXISTS, NOT BETWEEN, NOT IN etc. This is negate operator.

3

OR

The OR operator is used to combine multiple conditions in a PostgresSQL statement's WHERE clause.

PostgreSQL Bit String Operators

Bitwise operator works on bits and performs bit-by-bit operation. The truth table for & and | is as follows −

p q p & q p | q
0 0 0 0
0 1 0 1
1 1 1 1
1 0 0 1

Assume if A = 60; and B = 13; now in binary format they will be as follows −

A = 0011 1100

B = 0000 1101

-----------------

A&B = 0000 1100

A|B = 0011 1101

~A  = 1100 0011

Show Examples

The Bitwise operators supported by PostgreSQL are listed in the following table −

Operator Description Example
& Binary AND Operator copies a bit to the result if it exists in both operands. (A & B) will give 12 which is 0000 1100
| Binary OR Operator copies a bit if it exists in either operand. (A | B) will give 61 which is 0011 1101
~ Binary Ones Complement Operator is unary and has the effect of 'flipping' bits. (~A ) will give -61 which is 1100 0011 in 2's complement form due to a signed binary number.
<< Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand. A << 2 will give 240 which is 1111 0000
>> Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand. A >> 2 will give 15 which is 0000 1111
# bitwise XOR. A # B will give 49 which is 0100 1001


Advertisements