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Name ResolutionIn potentially uncertain SQL statements, the names of the database columns take precedence over the names of the local variables and formal parameters. For e.g. the DELETE statement removes all the employees from the emp table, not just ’KING’, as Oracle suppose that both enames in the WHERE clause refer to thedatabase column:DECLAREename VARCHAR2(10) := ’KING’;BEGINDELETE FROM emp WHERE ename = ename;In such cases, to avoid the uncertainty, prefix the names of the local variables and formal parameters with my_, as shown below:DECLAREmy_ename VARCHAR2(10);Or, use a block label to qualify references, as in<>DECLAREename VARCHAR2(10) := ’KING’;BEGINDELETE FROM emp WHERE ename = main.ename;The next illustration shows that you can use a subprogram name to qualify references to a local variables and formal parameters:FUNCTION bonus (deptno IN NUMBER, ...) RETURN REAL ISjob CHAR(10);BEGINSELECT ... WHERE deptno = bonus.deptno AND job = bonus.job;
SQLs counterpart of the key words: The text from the opening parenthesis to the end of the fourth line specifies the declared type of the table, meaning that every table ever
Expressions An expression is a randomly complex combination of the constants, variables, literals, operators, & function calls. The simplest expression is the single variabl
An analyst in the quality assurance office reviews the time lapse between receiving an order and shipping an order. Any orders that have not been shipped within a day of the order
UNION ALL - SQL Further varieties of UNION arise when we replace the key word DISTINCT by ALL in any of the foregoing examples, as in Example. ALL specifies that if row r appe
Relational Operators The relational operators permit you to compare randomly complex expressions. The list below provides the meaning of each operator:
Fetching from a Cursor Variable The FETCH statement retrieve rows one at a time from the product set of a multi-row query. The syntax for the same is as shown: FETCH {curso
First Step at defining type SID in SQL CREATE TYPE SID AS ( C VARCHAR(5) ) ; Explanation: TYPE SID announces that a type named SID is being defined to the syst
Cursor Variables As Parameters You can declare the cursor variables as the formal parameters of the functions and procedures. In the illustration below, you define the REF CUR
Use of COUNT in SQL It describes and discusses various general methods of expressing constraints, eventually noting that support for "=" with relation operands is sufficient f
Using the Collection Methods The collection methods below help to generalize the code and make collections easier to use and also make your applications easier to maintain:
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