PostgreSQL – Operators
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 −
|+||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 −
|=||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|
The AND operator allows the existence of multiple conditions in a PostgresSQL statement’s WHERE clause.
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.
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|
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 −
|&||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|
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