1. Overview The EXISTS condition in Oracle is a powerful operator used in SQL queries to check whether a subquery returns any rows. If the subquery returns at least one row, the EXISTS condition evaluates to TRUE; otherwise, it evaluates to FALSE. This feature is commonly used in scenarios requiring existence checks or correlated subqueries.…

1. Overview An anti-join in Oracle is used to find rows in one table that do not have matching rows in another table. It is essentially the opposite of a semi-join. Anti-joins are often implemented using the NOT EXISTS, NOT IN, or LEFT JOIN … IS NULL constructs. Anti-joins are particularly useful for identifying unmatched…

1. Overview A semi-join in Oracle is a type of query where rows from one table are returned if they satisfy a condition with at least one row from another table. Unlike regular joins, a semi-join only returns rows from the first table, even if multiple matching rows exist in the second table. It is…

1. Overview An outer join extends the result of a simple join. An outer join returns all rows that satisfy the join condition and also returns some or all of those rows from one table for which no rows from the other satisfy the join condition. An OUTER JOIN in Oracle retrieves rows from two…

1. Overview An inner join (sometimes called a simple join) is a join of two or more tables that returns only those rows that satisfy the join condition. An equi join is a subset of inner join that specifically uses the equality operator (=) in the join condition. In Oracle, an INNER JOIN is used…

1. Introduction The Cartesian product (or cross join) in Oracle SQL is the result of joining every row from one table with every row from another table. This type of join is typically unfiltered, meaning there’s no condition to match rows between the two tables. 2. Key Characteristics of Cartesian Product 3. Syntax Using CROSS…

1. Introduction A band join is a special type of nonequijoin in which key values in one data set must fall within the specified range (“band”) of the second data set. The same table can serve as both the first and second data sets. A Band Join in Oracle is a type of join where rows from…

1. Overview An equijoin is a join with a join condition containing an equality operator. An equijoin combines rows that have equivalent values for the specified columns. Depending on the internal algorithm the optimizer chooses to execute the join, the total size of the columns in the equijoin condition in a single table may be…

1. Introduction 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. If any two of these…

1. Introduction In Oracle Database, both the SYS and SYSTEM users are administrative accounts, but they have different roles and responsibilities. We’ll briefly discuss these two accounts. 2. SYS Account 3. SYSTEM Account 4. Key Differences In practice, the SYS account is reserved for system-critical tasks, while the SYSTEM account is more commonly used for…