String concatenation operator|| concatenates two strings together; for example, 'My name is'||' '||'Joe' returns the string My name is Joe.
Set operators Set operators allow concatenation of results from two queries. UNION ALL returns all rows including duplicates, UNION returns all unique rows, INTERSECT returns all rows common to both queries, and MINUS returns all rows in one and not the other query.
Hierarchical query operator The PRIOR operator placed with the CONNECT BY clause links the current row with a parent row.
