Join is a query which retrieves related columns or rows from multiple tables.Self Join - Joining the table with itself.Equi Join - Joining two tables by equating two common columns.Non-Equi Join
Latest Answer: In Full Outer Join we get both matched and unmatched data from both the tables whereas Cartesian join is a join in which each row of one table is cross multiplied with each row of the second table ...
Sub query is a query whose return values are used in filtering conditions of the main query.
Latest Answer: Hi Guys,A subquery is a SELECT statement that is embedded in a clause of another SQL statement, Called the parent statement.The subquery (inner query) returns a value that is used by the parent statement. Using a nested subquery is equivalent to performing ...
Correlated sub query is a sub query which has reference to the main query.
Latest Answer: Hi Guys,The Oracle Server performs a correlated subquery when the subquery references a column from a table reffered to in the parent statement. A correlated subquery is evaluated once for each row processed by the parent statement. The parent statement ...
Retrieves rows in hierarchical order.e.g. select empno, ename from emp where.
Latest Answer: select a.*, level from emp astart with mgr is nullconnect by mgr = prior empno ...
INSTR (String1,String2(n,(m)),INSTR returns the position of the mth occurrence of the string 2 instring1. The search begins from nth position of string1.SUBSTR (String1 n,m)SUBSTR returns a character
Latest Answer: substr is used to get a part of given string,instr is used to search a charcter in the given string.select substr(ename,1,3) three_charename, instr(ename,'A',1) a_present_at from emp; ...
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
Latest Answer: union: distinct result set of two queries.union all : result set of two or more queries including duplicatesminus: result set of first query "-" resultset of second queryintersect : common result set of both query; ...
ROWID is a pseudo column attached to each row of a table. It is 18 character long, blockno, rownumber are the components of ROWID.
Latest Answer: rowid is a unique value assigned by system automatically when ever a insert statement gets successful.rowid contains the address of data file,data block, object id, rownumber ...
Using ROWID.CONSTRAINTS
Latest Answer: by using the index and rowid ...
Integrity constraint is a rule that restricts values to a column in a table.
Latest Answer: Integrity constraint restricts values of a column so that only meaningful values as per the business logic of the table be entered into the column.Integrity constraints are of the following types:Not nullUniquePrimary KeyForeign Key (referential integrity)Check ...
Maintaining data integrity through a set of rules that restrict the values of one or more columns of the tables based on the values of primary key or unique key of the referenced table.
Latest Answer: foreign key constraints is know as referential integrity. which refers to a primary or ( unique ,not null) column ...
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