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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.
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
Renaming Columns - SQL SQL has no direct counterpart of RENAME. To derive the table on the right in Figure 4.4 from the table on the left, Tutorial D has IS_CALLED RENAME ( St
#quesWrite a cursor to open an employee database and fetch the employee record whose age is greater than 45.tion..
Wrapping and unwrapping in SQL Operators WRAP and UNWRAP in connection with attributes whose declared types are tuple types. Example shows how extension and projection can be
Relational Operators and Logical Operators It prepares the ground for subsequent sections in which each specific relational operator is paired with its logical counterpart, su
What are the rates for help in writing PL/SQL procedures and functions?
Built-In Functions The PL/SQL provides a lot of powerful functions to help you to manipulate the data. These built-in functions fall into the categories as shown below: error r
Creating a Table Syantax: CREATE TABLE ENROLMENT (StudentId SID, Name VARCHAR (30) NOT NULL, CourseId CID, PRIMARY KEY (StudentId, CourseId)) ; Explan
Scoping Within the similar scope, all the declared identifiers should be unique. So, even if their datatypes differ, the variables and parameters cannot share the similar name.
DELETE Command - SQL Loosely speaking, DELETE removes some existing rows from its target table. Suppose the university decides that course C3 is to be withdrawn. Example shows
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