The Else keyword defines the true or false condition in the case statement.The case statement’s conditional expression is most important to display the result. If one condition fails, the trigger goes to the second if it is true, it will display the result of the first condition. We can use a condition statement to retrieve the result of the data.When and then, the keyword is used to formulate the condition of the case statement.How does the CASE statement work in PostgreSQL? The flowchart is most important and useful while creating a case statement in PostgreSQL.
The flowchart is the pictorial representation of a case statement we have used in our query. Before executing any case statement, we need to define the flowchart of the case statement. If the condition is false, then the cursor directly goes to the end statement. If the given condition is true, it will execute a statement we wrote in the case statement. After that cursor goes to a condition we used in the statement. Normally we use a case keyword to start the case statement. The above flowchart states that the case statement starts with the case or starts with a keyword. The below diagram shows the flowchart of the case statement. Value 1 and 2: Value is nothing but a condition in the case statement. The body of the case statement will start with the case and end with the END keyword. End: We can end the case statement in PostgreSQL by using the end keyword. If the case statement condition is false, then the else part will execute otherwise, it is not executing. Else: Else keyword defines the true or false condition in the case statement. Result 1 to Result N: This is the actual result of the case statement in PostgreSQL. If one condition fails, the trigger goes to the second if it is true, it will display the result of all conditions. Condition 1 and 2: We can retrieve the data’s result using a condition statement. Then: Then, a keyword is used to formulate the condition of the case statement in PostgreSQL. 
When: When the keyword is used to formulate the condition of the case statement in PostgreSQL. Case: We can start the case statement in PostgreSQL by using a case keyword. (We can use multiple conditions in one case statement)īelow is the parameter description of the above syntax. result_2 (Result of second case statement). WHEN(When keyword used to formulate the condition) value_2 THEN(Then keyword used to formulate the condition). result_1(Result of first case statement). WHEN (When keyword used to formulate the condition)value_1 THEN(Then keyword used to formulate the condition). The below syntax shows simple case expression. (If the case statement result fails, then execute this statement). (We can use multiple conditions in one case statement). WHEN (When keyword used to formulate the condition)condition_2 THEN(Then keyword used to formulate the condition)result_2 (Result of second case statement). WHEN (When keyword used to formulate the condition) condition_1 THEN(Then keyword used to formulate the condition)result_1 (Result of first case statement). The below syntax shows a general case expression. WHERE CASE WHEN x 0 THEN y/x > 1.Below is the syntax of the case statement. For example, this is a possible way of avoiding a division-by-zero failure: The example above can be written using the simple CASE syntax:Ī CASE expression does not evaluate any subexpressions that are not needed to determine the result. This is similar to the switch statement in C. If no match is found, the result of the ELSE clause (or a null value) is returned. The first expression is computed, then compared to each of the value expressions in the WHEN clauses until one is found that is equal to it. There is a “ simple” form of CASE expression that is a variant of the general form above: The data types of all the result expressions must be convertible to a single output type. If the ELSE clause is omitted and no condition is true, the result is null. If no WHEN condition yields true, the value of the CASE expression is the result of the ELSE clause. If the condition's result is not true, any subsequent WHEN clauses are examined in the same manner. 
If the condition's result is true, the value of the CASE expression is the result that follows the condition, and the remainder of the CASE expression is not processed. Each condition is an expression that returns a boolean result. The SQL CASE expression is a generic conditional expression, similar to if/else statements in other programming languages:ĬASE clauses can be used wherever an expression is valid.
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