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 −
| 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 −
| 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.
| S. No. | Operator & Description |
|---|---|
| 1 | ANDThe AND operator allows the existence of multiple conditions in a PostgresSQL statement’s WHERE clause. |
| 2 | NOTThe 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 | ORThe 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
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 00110001 |