Table of Contents
How do you use conditionals in SQL?
Any T-SQL statement can be executed conditionally using IF… ELSE. If the condition evaluates to True, then T-SQL statements followed by IF condition in SQL server will be executed. If the condition evaluates to False, then T-SQL statements followed by ELSE keyword will be executed.
Can you use or statements in joins?
If you have an OR condition in the JOIN – and there is no possibility that the values in the OR statement overlap…then you can convert it to a UNION ALL. If the values overlap it would require a UNION which may not improve performance over the JOIN.
How do you write an if statement in SQL Select query?
You can have two choices for this to actually implement:
- Using IIF, which got introduced from SQL Server 2012: SELECT IIF ( (Obsolete = ‘N’ OR InStock = ‘Y’), 1, 0) AS Saleable, * FROM Product.
- Using Select Case : SELECT CASE WHEN Obsolete = ‘N’ or InStock = ‘Y’ THEN 1 ELSE 0 END as Saleable, * FROM Product.
How many else clauses can an if statement have?
An IF statement can have any number of ELSIF clauses; the final ELSE clause is optional. Boolean expressions are evaluated one by one from top to bottom. If any expression returns TRUE , its associated sequence of statements is executed and control passes to the next statement.
How many tables can be join in SQL query?
Theoretically, there is no upper limit on the number of tables that can be joined using a SELECT statement. (One join condition always combines two tables!) However, the Database Engine has an implementation restriction: the maximum number of tables that can be joined in a SELECT statement is 64.
Which of the following is the basic approaches for joining tables?
Discussion Forum
| Que. | Which of the following is one of the basic approaches for joining tables? |
|---|---|
| b. | Union Join |
| c. | Natural join |
| d. | All of the above |
| Answer:All of the above |
Which SQL JOIN is used for joining the table itself Mcq?
A self join is a regular join, but the table is joined with itself.
What is Theta join in SQL?
Theta Join allows you to merge two tables based on the condition represented by theta. Theta joins work for all comparison operators. It is denoted by symbol θ. The general case of JOIN operation is called a Theta join.
What are conditional joins in SQL Server?
Conditional Joins in SQL Server. Sometimes, when writing SELECTs, we come across situations in which we we need to write a join containing a condition of some sort, so that the join processed will vary for each row depending on the data.
How can I change the inner join’s relation from row to row?
There’s a much better way to approach the problem. Instead of trying to alter a single INNER JOIN’s relation from row to row, instead use multiple LEFT OUTER JOINS in your SELECT, one for each table or condition that you need to consider.
How do you connect multiple tables based on a common key?
If you have used Microsoft T-SQL at all you have undoubtedly used JOINS to connect multiple tables based on a common key value. You have probably also used the CASE statement functionality in your SELECT to conditionally change the output based on a set of parameters.
How to distinguish between two tables in a query?
The first two would be to use a Cross Apply against either a table valued function or against an Union and the third would be to simply use an Union as a sub-query with an added field to distinguish between the two tables and adding the proper condition to the ON statement. Sylvain Lafontaine, ing.