In the above query, you must specify the name of the table. Also, you need to mention each condition for which you want to check a particular column, just in case. End of declaration. You must also specify the value to assign to the column if each condition is true, that is, for each case. In this case, we would use CASE with no comparison value and specify the expressions/conditions to evaluate in the WHEN statements. In the following example, CASE is not satisfied with any of the WHEN values, it returns NULL. Let`s examine the data in the table after executing the UPDATE statement. Now we see the CASE statement, which looks quite similar to the CASE function but works differently. By the end of this guide, you will also know the difference between the CASE function and the CASE statement. The CASE statement traverses the conditions and returns a value if the first condition is met (for example, an IF-THEN-ELSE statement). Thus, once a condition is true, it stops reading and returns the result.
Note that if none of the case statements for a value are met, the CASE statement returns NULL. Here is an example in the following statement is CASE 1, so “this is the first case” is returned. The expression CASE returns a result whose data type depends on the context in which it is used. For example, if the CASE expression is used in the string context, it returns the result as a string. When used in a numeric context, the CASE expression returns the result as an integer, decimal, or real value. The MySQL CASE statement is different from the CASE function. MySQL CASE can also be used for conditional table updates. For example, in scenarios where you want to update the data in an existing column based on certain existing conditions or column values, you can assign the column to be updated to the CASE statement, which can be evaluated against various conditions and expressions.
Here, we used the expression CASE in a query with a CHAR_LENGTH() function that counts the number of characters of each name. Next, the WHEN block compares the specified values with the recently calculated value from the CHAR_LENGTH() function and returns the number in Word format. In the example above, the CASE statement returns NULL for 100 because it does not meet any of the conditions. Note that the CASE statement ends with END CASE instead of just END and cannot contain an ELSE NULL clause. This tutorial explains what the MySQL CASE statement is, when it is used, how to use it with the update statement, and when the statement in programs: The CASE statement for stored programs implements a complex conditional construct. Here, we created a stored procedure with a variable named `var` and assigned it to the default value of 1. Next, the variable `var` is compared to the digits in the WHEN block, and once a match occurs, the corresponding THEN block is executed and the CASE statement terminates. In our case, `var` is initialized with one so that the first WHEN block is executed and the output is displayed as `one`. It is important to note here that you mark the end of the CASE statement and that END CASE must be specified when you have specified all WHEN blocks.
Here is the step-by-step guide to the CASE function and the CASE statement, in which we went through their syntax and examples. We also understood that the two are different and can be used in different scenarios. If you think we missed something, let us know below. Be sure to exit the CASE function with the END keyword. Otherwise, an error is displayed. In MySQL, the CASE statement has the functionality of an IF-THEN-ELSE statement and has 2 syntaxes that we will explore. In MySQL, the CASE statement is used to apply a complex conditional construct in a stored program. Here we have given no value and no compare_value. Instead, we can write conditions such as the IF statement in the WHEN block and the corresponding results in the THEN block. Each statement_list consists of one or more SQL statements.
Empty statement_list is not allowed. This becomes clearer with the examples discussed as part of this tutorial. For the second syntax, each WHEN clause search_condition expression is evaluated until one of them is true, after which the corresponding THEN clause statement_list executed. If no search_condition is the same, the ELSE clause is executed statement_list, if applicable. Note: The syntax of the CASE expression shown here is slightly different from that of the CASE CASE SQL statement Syntax for stored programs. The CASE statement cannot have an ELSE NULL clause and ends with END CASE instead of END. In this tutorial, we will explore the MySQL CASE function. What`s interesting is that MySQL also offers the CASE statement, whose syntax is almost identical to the CASE function, but these are used for different use cases.
So we will see both; Function and instruction, with simple, easy-to-understand examples. The CASE() function in MySQL is used to find a value by passing conditions when a condition satisfies the specified statement, otherwise the statement is returned in another part. However, if a condition is met, it continues to stop playback and returns the output. Thread Stackoverflow on the case vs statement case function. In the following example, because condition 2>3 is FALSE, it returns the ELSE part, that is, “this is false”. If no when_value or search_condition matches the value being tested, and the CASE statement does not contain an ELSE clause, the CASE statement fails as a query. The CASE function must be part of an expression such as a query or assignment. However, the CASE statement cannot be used in a query because the query does not contain a statement.
For the first syntax, case_value is an expression. This value is compared to the when_value expression of each WHEN clause until one clause equals. If an equal when_value is found, the corresponding THEN clause is executed statement_list. If no when_value is the same, the ELSE clause is statement_list executed, if applicable. Here you can see that we used `grade` as a comparator with the CASE keyword and with the individual WHEN statements to which we specified the value of GRADE to compare. Example 1: Using the CASE() function and retrieving the output. This form of the CASE statement is used when you want to evaluate various complex expressions with WHEN statements.