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Variable Declaration - SQL
SQL's support for variables is very similar to Tutorial D's, except that the syntax for creating persistent variables-base tables-is quite different from that used to declare local variables. Example is SQL's counterpart of that example in the theory book but, as you know, CREATE TABLE is used for base tables.
Example: A Variable Declaration
DECLARE SN SID DEFAULT SID ('S1');
DECLARE in place of VAR and DEFAULT in place of INIT. The effect is exactly the same apart from the fact that, as already noted, SQL's type SID (here assumed to be a distinct type). The key word DEFAULT is perhaps a strange choice as that word normally suggests action to be taken by the system when no specific action is explicitly demanded by the user. Here it is used to state explicitly an immediate assignment to the variable being declared.
How Exceptions Propagate ? Whenever an exception is raised, and if the PL/SQL cannot find a handler for it in the present subprogram or block, the exception propagates. That is
Natural Join - SQL In the absence of NATURAL JOIN Example has to be replaced by something rather more longwinded, as shown in Example. Example: Joining IS_CALLED and IS_EN
Use of Table Expressions - Expressing Constraint Conditions With the exception of key constraints, the examples in the theory book all explicitly reference at least one relvar
Overloading The PL/SQL overloads the subprogram names. That is, you can use similar name for few different subprograms as long as their formal parameters differ in the number
Parameter and Keyword Description: select_item: This select_item is a value returned by the SELECT statement, and then assigned to the equivalent variable or field in the
Boolean Values Only the values TRUE, FALSE, & NULL can be assigned to a Boolean variable. For illustration, given the declaration DECLARE done BOOLEAN; the following statements
Using COUNT The COUNT returns the number of elements that a collection presently contains. For instance, when a varray projects contains 15 elements, then the following IF con
Iteration Schemes The bounds of a loop range can be variables, literals, variables, or expressions but must compute to integers. Below are some of the examples. As you can see t
Dynamic SQL: The Most PL/SQL programs do a predictable, specific job. For illustration, a stored procedure may accept an employee number and salary increase, and then update t
Explicitly specifying the join condition - SQL SELECT * FROM IS_CALLED JOIN IS_ENROLLED_ON ON ( IS_CALLED.StudentId = IS_ENROLLED_ON.StudentId ) Now, the key word JO
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