Introduction to Oracle CASE expression You can use a CASE expression in any statement or clause that accepts a valid expression. For example, you can use the CASE expression in statements such as SELECT, UPDATE, or DELETE, and in clauses like SELECT, WHERE, HAVING, and ORDDER BY.
Can I use CASE statement in WHERE clause?
CASE can be used in any statement or clause that allows a valid expression. For example, you can use CASE in statements such as SELECT, UPDATE, DELETE and SET, and in clauses such as select_list, IN, WHERE, ORDER BY, and HAVING.
Can we use case in WHERE condition in SQL?
CASE STATEMENT IN WHERE CLAUSE: The CASE statement returns the value based on condition. We can use a case statement in Where, Order by and Group by clause. So, by using a CASE statement with the where condition displays the result.
How does case work in Oracle?
In a simple CASE expression, Oracle Database searches for the first WHEN THEN pair for which expr is equal to comparison_expr and returns return_expr. If none of the WHEN THEN pairs meet this condition, and an ELSE clause exists, then Oracle returns else_expr.
Can we use alias in WHERE clause Oracle?
You can use the alias in GROUP BY, ORDER BY, or HAVING clauses to refer to the column: Standard SQL disallows references to column aliases in a WHERE clause. This restriction is imposed because when the WHERE clause is evaluated, the column value may not yet have been determined.
How do you put two conditions in a case statement in SQL?
Here are 3 different ways to apply a case statement using SQL:
- (1) For a single condition: CASE WHEN condition_1 THEN result_1 ELSE result_2 END AS new_field_name.
- (2) For multiple conditions using AND: CASE WHEN condition_1 AND condition_2 THEN result_1 ELSE result_2 END AS new_field_name.
What does exists do in SQL?
The EXISTS operator is used to test for the existence of any record in a subquery. The EXISTS operator returns TRUE if the subquery returns one or more records.
Is SQL case sensitive?
SQL Server is, by default case insensitive; however, it is possible to create a case sensitive SQL Server database and even to make specific table columns case sensitive. The way to determine a database or database object is by checking its “COLLATION” property and look for “CI” or “CS” in the result.
Can we use CASE statement in update query?
I have SQL server Table in which there is column that I wanted to update according to a 2 columns value that are present in current row. In this scenario, we can use CASE expression. CASE statement works like IF-THEN-ELSE statement.
Does a CASE statement need an else?
The CASE statement always goes in the SELECT clause. CASE must include the following components: WHEN, THEN, and END. ELSE is an optional component.
How many nested IF clauses can be included within an if clause?
Answer B is correct. You can only have one ELSE clause for every IF clause. If the IF clause is not nested, there is only one.
Can CASE statement return multiple values?
@yzhang – With CASE only the first match will return values. If you want the possibility of multiple conditions mathcing each input row, you need to make each check indpendantly, and UNION the results together.
Are column aliases allowed in FROM clause?
Table Alias. Table aliases can be used in SELECT lists and in the FROM clause to show the complete record or selective columns from a table. Table aliases can be used in WHERE, GROUP BY, HAVING, and ORDER BY clauses.
Can we use alias name in WHERE clause in SQL Server?
column_alias can be used in an ORDER BY clause, but it cannot be used in a WHERE, GROUP BY, or HAVING clause. Standard SQL disallows references to column aliases in a WHERE clause.
Can you GROUP BY an alias in SQL?
Aliases can be used only if they were introduced in the preceding step. So aliases in the SELECT clause can be used in the ORDER BY but not the GROUP BY clause. Reference: Microsoft T-SQL Documentation for further reading.