CASE Statement in SQL (Practical Examples)

Table of contents:

• Tell me the best way to use SQL statement?
• Performance tuning simple case expression data
• SQL Case statement with the following query
• SQL Server: CASE Statements or Case expression
• If Then Else Statement with SQL Server
• The Searched CASE Expression SQL Statement
• Simple CASE Statement with SQL Server and Order by clause
• Nesting SQL Case statement
• How do I write a case end sql?
• What is SQL Server CASE Statement?
• How do you exit a case statement in the following query?
• Can you use CASE statement in join condition?
• Can an OR statement have a join in else clause?
• Is SQL CASE statement supported in SQL Server?

If you have ever visited Mysql's documentation OR SQL Server's documentation about a case statement, you may have been as lost as I was. You will find something like this that contains a boolean expression:

CASE vWHEN 2 THEN SELECT v;
WHEN 3 THEN SELECT 0;
ELSE
BEGIN
END;
END CASE;

Tell me the best way to use SQL statement?

If you are as confused as I was, let me provide you a better, more clear data example of a case statement using sql server values.

Let's break down what's happening in the case statement above. It's analyzing the variable "v" with SQL server. When v is equal to 2, it will return "v", if it's 3, it will return "0", otherwise it will do nothing when this case statement is executed.

Performance tuning simple case expression data

Let's apply this to more realistic case statement example with SQL server. In the execution flow of the searched case, let's say we have a state field and a country field, but we only want to show the state if the country is USA. We could write something like this in descending order:

SELECT first, last, country,CASE country WHEN 'USA' THEN state ELSE 'Outside USA' END as state
FROM users

SQL Case statement with the following query

In the above example using SQL server for our case statement, if our country is USA it will return the actual state, otherwise it will return Outside USA. Hopefully this provides a clear idea of where this can be used. I will now should a much more complex case statement example with SQL Server. This is something I have used to create a message center that displays the most recent message in the summary for the searched case example query.

SELECT m1.* FROM messages m1LEFT JOIN messages m2 ON
 CASE WHEN m1.idparent = 0 THEN
  CONCAT(m1.idmessage, CHAR(45), m1.idparent) ELSE m1.idparent END = m2.idparent
  AND m1.idmessage < m2.idmessage
WHERE m2.idmessage IS NULL
AND m1.receiver_id = 1
ORDER BY m1.datesent DESC

SQL Server: CASE Statements or Case expression

The following query will return all messages for receiver_id = 1. By joining the messages table to itself it will allow us to retrieve the most recent content to display. This is a simple case expression example query.

Let's analyze this more. First off, we our doing a left join because not all messages will have children messages (or a reply), so if nothing is found it will return the main record.

If Then Else Statement with SQL Server

(Don't forget to End Your If…sorry couldn't resist)

Case statement in sql can be a specific else clause in SQL server return arbitrary number of values based upon specific conditions in SQL. It is possible in some queries to include a case statement as well as clauses where, order by and group by. Same is also possible for inserting a statement. In this section, we will examine the CASE statement and their different usage cases. Show me the product ID on each table. Get Product Name for the Product ID. Please see the following example. We created a variable @ProductID and specified 1 to it in the sql statement. In case statements, the conditions are described, for example, an employee table. Once conditions are met, the null values will be returned in the else clause of the sql case statement.

The Searched CASE Expression SQL Statement

Our actual JOIN condition with the following syntax takes care of ensuring it returns us the most recent content. It does this by doing a case statement. If the parent id is 0 this means it is the first record in the thread, to ensure it's a unique and won't return every other first record in the thread we concatenate the message id and the parent id together separated by a "-". Otherwise, if the message is a child we join it to all of the other child threads. We then proceed to ensure that the message id being returned is less than the highest message id.

Hopefully the above ramble is clear, it's sometimes hard to explain this kind of logic and hopefully it will enable you to successfully use CASE statements in your future work!

Simple CASE Statement with SQL Server and Order by clause

Searchable case statements have probably been used more in recent years as they have been extremely flexible but they have other formats, called simple CASE statements or if then else statement with an equality check. The examples patterns are similar to switches commonly found in programming languages or the DECODE function in other databases systems with the corresponding value. Shows the negative effects of simple CASE statements in an update statement without an order by clause.

It's been added to MySQL 2012 to include a t-sql (transact SQL) language IIF (searched case statement). This shorthand means searched for CASEs if there are search queries with null values. Let's change what we've done: Use of IIF, becomes a value query or a select case example: Adding IIF results into compact programming languages. In some cases, unlike DAX, false branch IIF is optional but always specified in the sql server community.

Nesting SQL Case statement

The search case expression allows for multiple conditions - when: You can even create an entirely different case expression in an argument. The simplest SQL statement in T sql (transact sql) is one with multiple nested CASE expressions.

SQL Server (Transact SQL) The CASE statement uses a function that translates to an IF statement. The CASE statements may be used that conditions sequentially or ascending order with the select count data types in a second case statement example.

How do I write a case end sql?

SQL Server CASE statements need inclusion in SECTIONS select case or other languages with an order by clause. It starts with the CASE keywords, then the WHEN and the CONDITION. This condition could include any SQL Server expression that returns the Boolean value.

What is SQL Server CASE Statement?

SQL CASE Statements:

CASE statements go through corresponding conditions and return a value if the first condition is satisfied. Once conditions are true, it stops reading and returns results as well. If a condition is false the value is returned by the clause ESE.

How do you exit a case statement in the following query?

Use the if clause or the else statement inside the case to avoid any other conditions in the above example. Programs with a good structure are what we are looking for in sql server!

End is a marker to close CASE Expressions. There should be one final sql case statement with each scenario statement. AS markers are prepositions allowing aliases. The aliases are: MissingItemAB or employee table with SQL Server.

Can you use CASE statement in join condition?

In these few examples, conditional columns join can be a fancy way to join a single and multiple columns together. The way it will be possible is to add case statement to a when clause. Joins with the execution flow and the having clause that can be used with aggregate functions to return from Microsoft SQL Server in descending order. SQL case statement allow us to evaluate multiple conditions in a given situation for producing one value.

Case statement in SQL Syntax. If you have a single condition you can specify WHEN followed by a condition that needs to be fulfilled. Those are the keywords AND the value for this condition. Those words then follow another WHEN / THEN statement with SQL Server.

Can an OR statement have a join in else clause?

If the condition OR in the statement is not possible that the values in the statement are overlapped then it is possible for them to become ONE. The overlap in values requires UNIONS to perform better.

The Conditional Column Join is an interesting method for combining the one column and two columns. Then use cases for joining. Case statements are used for testing multiple conditions (like if/else if) to produce one value.

A Join statement is a SET which combine data from 2 tables with a results table according to a condition known as join conditions.

Is SQL CASE statement supported in SQL Server?

A case statement in SQL returns a value to a specified condition in the above query. It may use case statements to select questions together with the clauses Where Order By and Group By inside stored procedures. It is also possible to insert column values with zero error in the then clause with a boolean expression. The select clause in your sql tables set statement can be a simple expression, single value, result expressions, or a select statement with a specific data type that can be used when performance tuning in the defined conditions in alphabetical order.

Case is an expression that allows a valid word. For instance CASE is a syntax used in statements such as select, update, delete, set and clause without a null end.

Published on Jul 9, 2022

Tags: SQL Tutorials for Beginners, Intermediate and Advanced Users | case | concat