![]() Remember, the END at the end of the CASE WHEN expression is important. This is how you can do it − SELECT name, CASE WHEN perc_marks >= 40 THEN 'PASS' ELSE 'FAIL' END Now, if the student has scored above 40 marks, we want to print ‘PASS’ against that student’s name, otherwise ‘FAIL’. If you have table marks containing percentage marks of a student, and you want to find out whether the students have passed or failed. The equivalent in PostgreSQL is CASE WHEN. from ( select CASE WHEN accountid IS NOT NULL THEN value ELSE value2 END AS result. You have to use a derived table: select result, result as result2. ELSE result END CASE clauses can be used wherever an expression is ndition is an expression that returns a boolean result. 1 Answer Sorted by: 0 You can't use a column alias on the same level where you define it. If you reverse the order of the first two conditions (i.e., if you specify WHEN result <= 70 THEN 'average result' first then WHEN result <= 70 THEN 'average result' second), all results less than or equal to 70 end up in the 'average result' category, with no results assigned to the 'bad result' category.If you are a programmer, you may be very familiar with IF-ELSE statements. The SQL CASE expression is a generic conditional expression, similar to if/else statements in other languages. Note: The order of the conditions in CASE matters. CASE WHEN in PostgreSQL PostgreSQL Database Data Storage If you are a programmer, you may be very familiar with IF-ELSE statements. Finally, for the remaining results the category should be 'good result' a simple ELSE 'good result' takes care of it. WHEN result >= 40 AND result = 40 AND result = 40 in specifying the conditions for the 'average result' – all results less than 40 already have the value 'bad result' assigned. ![]() Since 'average result' is assigned to results between 40 and 70 (inclusive), you may also write a condition instead of ELSE (see Solution 2 below). Also, to name the newly created column of the text values, you need to use an alias ( AS category). If neither of these conditions is met, the value is 'average result'. SELECT DD1409.ZIPCODE, count () RECORDS, (SUM ( (CASE WHEN GENDER 'F' then 1 else 0 end)) / count ()) 100 GENDERF, (SUM ( (CASE WHEN PRESENCEOFELDERLYPARENT 'Y' then 1 else 0 end)) / count ()) 100 PRESENCEELDERLYPARENTY, MEDIAN (LENGTHOFRESIDENCE), (SUM ( (CASE WHEN HOMEOWNERSTATUS 'P' then 1 else 0 end)) / c. Lets take a closer look at the construct of a Case statement and see other ways where it could be useful in PostgreSQL. In our example, 'bad result' is assigned when result 70. If you have table marks containing percentage marks of a student, and you want to find out whether the students have passed or failed. CASE The CASE expression goes through conditions and returns a value when the first condition is met (like an if-then-else statement). Of course, as with any column you create, you can rename it ( AS ). CASE WHEN in PostgreSQL PostgreSQL Database Data Storage If you are a programmer, you may be very familiar with IF-ELSE statements. 1 Answer Sorted by: 1 We can nest CASE expressions, or use multiple tests if appropriate. WITH provides a way to write auxiliary statements for use in a larger query. Remember to END the CASE clause when you're done with all of the conditions. Postgresql does not cast the output, and since you have an else condition, youre getting false. This provides flexibility in manipulating query components, such as table names, column names, conditions, and sorting. If the ELSE clause is omitted and no condition matches, the result is null. Understanding prepared statements Prepared statements refer to the ability to construct SQL statements dynamically at runtime rather than writing them statically in the code. If you omit it and none of the conditions are met, you get a NULL. As the PostgreSQL documentation states: If no WHEN condition is true then the value of the case expression is the result in the ELSE clause. ![]() If none of the conditions is met, the value_n specified after the ELSE is retrieved. If neither of these conditions is met, SQL checks for the remaining conditions one by one in order until one of the conditions is met. If condition_2 is true, then the retrieved value is value_2. If not, then the database checks for condition_2. If condition_1 is met, then the retrieved value is value_1. To display a value based on your specific condition(s), you need to write a CASE statement. Bad results are those below 40, good results are those above 70, and the rest are average results. You need to assign each result to one of the following text values: 'bad result', 'average result', or 'good result'.
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