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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.
Advantages of Subprograms The Subprograms give extensibility; that is, tailor the PL/SQL language to suit your requirements. For illustration, if you require a procedure which
ALTER TABLE bb_basketitem ADD CONSTRAINT bitems_qty_ck CHECK (quantity BEGIN INSERT INTO bb_basketitem VALUES (88,8,10.8,21,16,2,3); END; Brewbean’s wants to add a check
Tautology - Equivalences Rules: If there Tautologies are not all the time as much easy to note as the one above so than we can use these truth tables to be definite that a sta
Extension and AND in SQL The theory book gives the following simple example of relational extension in Tutorial D: EXTEND IS_CALLED ADD ( FirstLetter ( Name ) AS Initial )
Example of EXCEPT Operator - SQL Example, like its counterpart in the theory book, illustrates the convenience of allowing any table expression to be the source for an INSERT
Explicit Cursor Attributes The cursor variable or each cursor has four attributes: %FOUND, %ISOPEN, %ROWCOUNT, and %NOTFOUND. When appended to the cursor or cursor variable, th
Package Body: The package specification is implemented by the package body. That is, the package body has the definition of every cursor and the subprogram declared in the pac
ROWID The ROWID returns the rowid (binary address) of a row in the database table. You can use the variables of the type UROWID to store rowids in a readable format. In the il
%FOUND Until the SQL data manipulation statement is executed, the %FOUND yields NULL. Afterward, the %FOUND yields TRUE, when an INSERT, UPDATE, or DELETE statement affected o
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
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