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    Operators

    Last updated: 2024-01-22 10:52:48
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      An operator is a reserved word or a character used primarily to specify conditions in a SQL statement and to serve as conjunctions for multiple conditions in a SQL statement.
      Mathematical Operators
      Comparison Operators

      Mathematical Operators

      Mathematical operators are symbols used to process four arithmetic operations. They are the simplest and most commonly used operators, especially for number processing. Almost all number processing involves mathematical operators.
      Assume variable a holds 1 and variable b holds 2, then:
      Operator
      Description
      Example
      + (Addition)
      Adds values on either side of the operator.
      a + b
      - (Subtraction)
      Subtracts the right hand operand from the left hand operand.
      a - b
      * (Multiplication)
      Multiplies values on either side of the operator.
      a * b
      / (Division)
      Divides the left hand operand by the right hand operand.
      b / a
      % (Modulus)
      Divides the left hand operand by the right hand operand and returns the remainder.
      b % a

      Comparison Operators

      Comparison operators are used to determine the size relationships of values and support any value type that can be compared, such as int, long, double, and text.
      Assume variable a holds 1 and variable b holds 2, then:
      Operator
      Description
      Example
      =
      Checks if the values of two operands are equal or not. If yes, the condition is true.
      a = b
      !=
      Checks if the values of two operands are equal or not. If no, the condition is true.
      a != b
      <>
      Checks if the values of two operands are equal or not. If no, the condition is true.
      a <> b
      >
      Checks if the value of the left operand is greater than the value of the right operand. If yes, the condition is true.
      a > b
      <
      Checks if the value of the left operand is less than the value of the right operand. If yes, the condition is true.
      a < b
      >=
      Checks if the value of the left operand is greater than or equal to the value of the right operand. If yes, the condition is true.
      a >= b
      <=
      Checks if the value of the left operand is less than or equal to the value of the right operand. If yes, the condition is true.
      a <= b
      IN
      The IN operator is used to compare a value with a specified list of values.
      status IN (200,206,404)
      NOT IN
      The NOT IN operator is used to compare a value with values that are not in a specified list. It is the opposite of the IN operator.
      status NOT IN (200,206,404)
      BETWEEN AND
      The BETWEEN operator tests if a value is within a specified range (BETWEEN min AND max).
      status between 200 AND 400
      LIKE
      The LIKE operator is used to compare a value with a similar value using the wildcard operator. The percent sign (%) represents zero, one, or multiple characters. The underscore (_) represents a single digit or character.
      url LIKE '%.mp4'
      IS NULL
      The NULL operator compares a value with NULL. If the value is null, the condition is true.
      status IS NULL
      IS NOT NULL
      The NULL operator compares a value with NULL. If the value is not null, the condition is true.
      status IS NOT NULL
      DISTINCT
      Syntax: x IS DISTINCT FROM y or x IS NOT DISTINCT FROM y.
      The DISTINCT operator checks if x equals to y. Unlike <>, it can compare nulls. For more information, see Differences between <> and DISTINCT.
      NULL IS NOT DISTINCT FROM NULL
      LEAST
      Syntax: LEAST(x, y...).
      Returns the minimum value among x,y...
      LEAST(1,2,3)
      GREATEST
      Syntax: GREATEST(x, y...).
      Returns the maximum value among x,y...
      GREATEST(1,2,3)
      ALL
      Syntax: x expression operator ALL ( subquery )
      Returns true if x meets all conditions. Supported operators are <, >, <=, >=, =, <>, !=.
      Example 1: 21 < ALL (VALUES 19, 20, 21)
      Example 2: * | SELECT 200 = ALL(SELECT status)
      ANY / SOME
      Syntax: x expression operator ANY ( subquery ) or x expression operator SOME ( subquery ).
      Returns true if x meets any condition. Supported operators are <, >, <=, >=, =, <>, !=.
      Example 1: 'hello' = ANY (VALUES 'hello', 'world')
      Example 2: * | SELECT 200 = ANY(SELECT status)
      
      Differences between <> and DISTINCT:
      
      x
      y
      x = y
      x <> y
      x IS DISTINCT FROM y
      x IS NOT DISTINCT FROM y
      1
      1
      true
      false
      false
      true
      1
      2
      false
      true
      true
      false
      1
      null
      null
      null
      true
      false
      null
      null
      null
      null
      false
      true
      
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