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    Operator                                         Description
                                   <               Checks if the left value is less than the right value.

                                   >               Checks if the left value is greater than the right value.

                                   <=              Checks if the left value is less than or equal to the right value.

                                   >=              Checks if the left value is greater than or equal to the right value.

                      LOGICAL OPERATORS

                      Logical operators are used to combine multiple conditions in a query. These operators allow
                      you to create complex queries. They include the following types:

                               Operator                                         Description

                       AND                         Returns TRUE if both conditions are true.
                       OR                          Returns TRUE if at least one condition is true.

                                                   Reverses the  logical  state  of its  operand,  returning TRUE  if the
                       NOT
                                                   condition is FALSE and vice versa.

                      SPECIAL OPERATORS

                      Some special operators in SQL are as follows:

                               Operator                                         Description

                       ALL                         Returns TRUE if all of the subquery values meet the condition.

                       ANY                         Returns TRUE if any of the subquery values meet the condition.
                                                   Used to indicate a range which otherwise is done using relational
                       BETWEEN
                                                   operators.
                       EXISTS                      Returns TRUE if the subquery returns one or more records.

                             SQL CONSTRAINTS

                      SQL  constraints are used  to  define  rules for table  data.  These rules control  the  data  that
                      can be stored in a column. Constraints are used to restrict the types of data that can be entered
                      into a table.

                      Some different types of constraints include:
                          NULL constraint: The NULL constraint allows a column to store NULL values. If no value is
                         provided during insert or update, it does not cause an error.

                          NOT NULL constraint: The NOT NULL constraint specifies that a column must have a value.
                         Records cannot be inserted or updated without providing a value for this column.

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