The CTE name is provided just after the WITH clause. The first part of the query is the part where we have defined the common table expression. Let us look at the query for the sameĬTE AS (SELECT name, employee_id FROM employee WHERE city = 'Delhi')Įxplanation: Now we will go through the query and understand it. In this example, we will create a single CTE which will have the result set of the employee id and employee name of the employees present in the employee table. We can create multiple CTEs in a single WITH clause. Examples to Implement Oracle CTEīelow are the examples mentioned: Example #1 – SINGLE CTE USING WITH CLAUSE One important point to remember while dealing with recursive CTE is that if it is not created properly it will create an infinite loop. It is mainly used when we are dealing with hierarchical data such as company hierarchy positions chart or table because the recursive CTE will continue executing until the entire hierarchy is returned in the result set. It has a sub query that refers to its own name. So we can say that the scope of the CTE is still the execution of the statement.Ī Recursive common table expression (RCTE) as the keyword recursive suggests references itself. Once the execution is done of the query we cannot use the CTE in any other statements or query. The most important point is that we can refer it in the scope of the execution of the WITH clause query. We can reference that defined CTE like we would reference a table in a database. So, once we define the CTEs by the use of WITH clause. We can add more than one CTE with a single WITH clause by separating them with the help of commas. Here statement means SELECT, INSERT, UPDATE, DELETE. So for the database to understand we define it using WITH clause before the starting of the CTE query statement. In this section, we are going to discuss about how it works in database. CTE query: It actually refers to the query or the statement.Īs we have already seen in the earlier section of this article about the definition of the CTE.column1: It refers to the column or column names of the table.CTE_NAME: It refers to the name we want to give the common table expression.Hadoop, Data Science, Statistics & others

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