Can we write SQL query in if condition?
Unlike other programming languages, you cannot add an ELSE IF statement within an IF ELSE condition in SQL. This is why you can nest IF ELSE in SQL query statements.
What is table hints in SQL Server?
SQL Server table hints are a special type of explicit command that is used to override the default behavior of the SQL Server query optimizer during the T-SQL query execution This is accomplished by enforcing a specific locking method, a specific index or query processing operation, such index seek or table scan, to be …
How do I use index hint?
Use the INDEX hint for function-based, domain, B-tree, bitmap, and bitmap join indexes. When working with tables containing ST_Geometry attributes and a st_spatial_index, specify the Oracle INDEX hint and the name of the st_spatial_index to instruct the optimizer to access the data by way of the index.
How do you use parallel hint in select statement?
SELECT /*+ PARALLEL(table_alias,Degree of Parallelism) */ FROM table_name table_alias; Let’s say a query takes 100 seconds to execute without using parallel hint. If we change DOP to 2 for same query, then ideally the same query with parallel hint will take 50 second. Similarly using DOP as 4 will take 25 seconds.
Can I use an IF statement in a select query?
Answer: MySQL IF() function can be used within a query, while the IF-ELSE conditional statement construct is supported to be used through FUNCTIONS or STORED PROCEDURES.
How do you write an if statement in a 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.
What does <> mean in database?
Not equal to
It (<>) is a function that is used to compare values in database table. != (Not equal to) functions the same as the <> (Not equal to) comparison operator. Follow this answer to receive notifications.
What is index hint in SQL Server?
Index hints are used to force a query to use a specific index, instead of allowing SQL Server’s Query Optimizer to choose what it deems the best index.
What are database hints?
In various SQL implementations, a hint is an addition to the SQL standard that instructs the database engine on how to execute the query. For example, a hint may tell the engine to use or not to use an index (even if the query optimizer would decide otherwise).
What is parallel hint in SQL?
Parallel SQL enables a SQL statement to be processed by multiple threads or processes simultaneously. Today’s widespread use of dual and quad core processors means that even the humblest of modern computers running an Oracle database will contain more than one CPU.
How do you write a parallel hint?
Statement-level parallel hints are the easiest: SELECT /*+ PARALLEL(8) */ first_name, last_name FROM employee emp; Object-level parallel hints give more control but are more prone to errors; developers often forget to use the alias instead of the object name, or they forget to include some objects.
How do you write nested if in SQL?
It is always legal in PL/SQL programming to nest the IF-ELSE statements, which means you can use one IF or ELSE IF statement inside another IF or ELSE IF statement(s).
Can we use if condition in where clause?
IF… ELSE clause is very handy and whenever you need to perform any conditional operation, you can achieve your results using it. But there are some limitations in IF… ELSE, and one of the limitations is that you cannot use it in WHERE clause.
What is SQL logical operator?
Logical operators are used to specify conditions in the structured query language (SQL) statement. They are also used to serve as conjunctions for multiple conditions in a statement. The different logical operators are shown below − ALL − It is used to compare a value with every value in a list or returned by a query.
What does <> this symbol mean in SQL?
not equal to operator
The symbol <> in MySQL is same as not equal to operator (!=). Both gives the result in boolean or tinyint(1). If the condition becomes true, then the result will be 1 otherwise 0.
How do I use hints in MySQL?
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- Comment syntax /*+ */ is used for the new hints.
- Multiple hints can be specified within the same comment.
- A query block can have only one comment containing hints, and that comment must directly follow the SELECT , UPDATE , INSERT , REPLACE , or DELETE keyword.
What is DB hint?
When you send a query to a database, the database engine works out how to execute that query using various heuristics. This usually results in an extremely efficient plan.
How do you use parallel hint in query?
Oracle Database Hints Parallel Hint SELECT /*+ PARALLEL(emp,8) */ first_name, last_name FROM employee emp; SELECT /*+ PARALLEL(table_alias,Degree of Parallelism) */ FROM table_name table_alias; Let’s say a query takes 100 seconds to execute without using parallel hint.
What is if statement in SQL Server?
Is any Transact-SQL statement or statement grouping as defined by using a statement block. Unless a statement block is used, the IF or ELSE condition can affect the performance of only one Transact-SQL statement.
What are query hints in SQL?
Query hints specify that the indicated hints are used in the scope of a query. They affect all operators in the statement. If UNION is involved in the main query, only the last query involving a UNION operation can have the OPTION clause. Query hints are specified as part of the OPTION clause.
How to nest if statements within another if statement in SQL Server?
SQL Server allows you to nest an IF…ELSE statement within inside another IF…ELSE statement, see the following example: First, declare two variables @x and @y and set their values to 10 and 20 respectively: Second, the output IF statement check if @x is greater than zero.
What is if condition in SQL with example?
Code language: SQL (Structured Query Language) (sql) Each IF statement has a condition. If the condition evaluates to TRUE then the statement block in the IF clause is executed. If the condition is FALSE, then the code block in the ELSE clause is executed. See the following example: