WHAT IS WITH clause in Oracle with example?
The SQL WITH clause was introduced by Oracle in the Oracle 9i release 2 database. The SQL WITH clause allows you to give a sub-query block a name (a process also called sub-query refactoring), which can be referenced in several places within the main SQL query.
Can we use with clause in Oracle?
With clause in oracle is not supported by all oracle versions ,the oracle version 9i and beyond versions. When sub-query needs to be executed multiple times at that time With clause is used. The name which is assigned to the sub-query is treated as though it was an inline view or table.
What does (+) mean in Oracle SQL joins?
The plus sign is Oracle syntax for an outer join. There isn’t a minus operator for joins. An outer join means return all rows from one table. Also return the rows from the outer joined where there’s a match on the join key.
What is connect by in Oracle?
CONNECT BY specifies the relationship between parent rows and child rows of the hierarchy. The NOCYCLE parameter instructs Oracle Database to return rows from a query even if a CONNECT BY LOOP exists in the data. Use this parameter along with the CONNECT_BY_ISCYCLE pseudocolumn to see which rows contain the loop.
What is the use of WITH clause?
WITH clause allows us to give a subquery block a name that can be used in multiple places within the main SELECT, INSERT, DELETE or UPDATE SQL query. The name assigned to the subquery is treated as though it was an inline view or a table. It is very helpful when you need the same set of results data multiple times.
Can we use with clause in subquery?
The WITH clause is for subquery factoring, also known as common table expressions or CTEs: The WITH query_name clause lets you assign a name to a subquery block. You can then reference the subquery block multiple places in the query by specifying query_name.
What is connect by clause?
The CONNECT BY clause specifies the relationship between parent rows and child rows of the hierarchy. The connect_by_condition can be any condition, however, it must use the PRIOR operator to refer to the parent row.
What is level in Connect by?
LEVEL is a pseudocolumn that returns the ordinal number of the recursive step in the Hierarchic clause that returned the row. For all the rows returned by the START WITH clause, LEVEL return the value 1 . Rows that are returned by applying the first iteration of the CONNECT BY clause return 2.
What is meaning of (+) in SQL?
Outer Join Operator (+)
Outer Join Operator (+) – Oracle to SQL Server Migration Oracle outer join operator (+) allows you to perform outer joins on two or more tables. Quick Example: — Select all rows from cities table even if there is no matching row in counties table SELECT cities. name, countries.
Can we join 2 views in Oracle?
A join is a query that combines rows from two or more tables, views, or materialized views. Oracle Database performs a join whenever multiple tables appear in the FROM clause of the query. The select list of the query can select any columns from any of these tables.
What is connect by root?
CONNECT_BY_ROOT is a unary operator that is valid only in hierarchical queries. When you qualify a column with this operator, Oracle returns the column value using data from the root row. This operator extends the functionality of the CONNECT BY [ PRIOR ] condition of hierarchical queries.