Sub-query is a query whose return values are used in filtering conditions of the main query.
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Ques 107. What is correlated sub-query?
Correlated sub-query is a sub-query, which has reference to the main query.
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Ques 108. Explain CONNECT BY PRIOR?
Retrieves rows in hierarchical order eg. select empno, ename from emp where.
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Ques 109. Difference between SUBSTR and INSTR?
INSTR (String1, String2 (n, (m)), INSTR returns the position of the m-th occurrence of the string 2 in string1. The search begins from nth position of string1. SUBSTR (String1 n, m) SUBSTR returns a character string of size m in string1, starting from n-th position of string1.
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Ques 110. Explain UNION, MINUS, UNION ALL and INTERSECT?
INTERSECT - returns all distinct rows selected by both queries. MINUS - returns all distinct rows selected by the first query but not by the second. UNION - returns all distinct rows selected by either query UNION ALL - returns all rows selected by either query, including all duplicates.