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CHECK Constraints in SQL
A CHECK constraint is a table constraint defined using the key word CHECK, as already illustrated in several examples in this chapter. In particular, a CHECK constraint can be used to express a constraint such as the one shown in Example, referred to in the theory book as a tuple constraint (so one might call it a row constraint in SQL). This is clearly the way most SQL users would prefer to express such a constraint.
Example of WHEN or THEN Constraints A concrete example showing how SQL supports WHEN/THEN constraints CREATE TABLE SAL_HISTORY (EmpNo CHAR (6), Salary INTEGER NOT NULL,
Cursor Attributes The Cursors and cursor variables have 4 attributes which give you helpful information about the execution of a data manipulation statement. Syntax:
what are ER diagrams
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Parameter and Keyword Description: SQL: This SQL is the name of the implicit SQL cursor. %FOUND: This attribute results TRUE if an INSERT, DELETE, or UPDATE state
Question: Consider the following relations (primary keys are underlined): AUTHOR (ANo, aname, address, speciality) PUBLISHER (PNo, pname, Location) BOOK (BNo, Title, ISBN,
Recursive Subprograms The recursive subprogram is the one that calls itself. Think of a recursive call as a call to a few other subprograms that does the similar task as your
SQL Pseudocolumns The PL/SQL recognizes the following SQL pseudocolumns, that returns the specific data items: LEVEL, NEXTVAL, CURRVAL, ROWID, & ROWNUM. The Pseudocolumns are n
Keyword and Parameter Description select_statement: This is a query which returns a result set of the rows. Its syntax is such that of select_ into_statement without the IN
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