Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
WHEN or THEN Key Constraints
Suppose a table has two columns representing a period of time throughout which the information conveyed by the other columns is recorded as having been the case. A salary history table for employees, with columns From and To for dates defining the applicable time periods, would be a good example.
A constraint is needed to avoid the possibility of an employee being shown as having two different salaries on the same day, which could happen if two rows for the same employee have overlapping periods indicated by their From and To dates. The term "WHEN/THEN constraint" appeals to the notion of "unpacking" the table so that each row is replaced by one or more rows, one for each date contained in its from-to period: when the relation is unpacked, then the given key constraint (e.g., on employee number and date) is to hold.
ROWNUM The ROWNUM returns a number representing the order in which a row was selected from the table. The first row selected has a ROWNUM of 1; the second row has a ROWNUM of
Read-Only Operator (+) - SQL The term read-only operator to the mathematical term function. Here I just need to add that the SQL standard reserves the term function for read-
Delimiters A delimiter is a simple or compound symbol which has a special meaning to PL/SQL. For example, you use delimiters to symbolize an arithmetic operation like additio
What are 3 good practices of modeling and/or implementing data warehouses?
Overloading: Similar to packaged subprograms, methods of the same type can be overloaded. That is, you can use similar name for various methods if their formal parameters diff
Data Types in SQL - Integer INTEGER or synonymously INT, for integers within a certain range. SQL additionally has types SMALLINT and BIGINT for certain ranges of integers. T
Use Native Dynamic SQL A few programs (a normal-purpose report writer for illustration) should build and process a variety of SQL statements at run time. Therefore, their full
PITS Depressions in secondary cell wall is called pit. A pit present on the free cell wall surface without its partner is called Blind pit. It consists of 2 parts -
Updating a Variable Assignment of an attribute value in a variable of a structured type Synatx: SET SN.C = 'S2'; As in Example the entire statement is equivalent to a
Short-Circuit Evaluation When computing a logical expression, the PL/SQL uses short-circuit evaluation. That is, the PL/SQL stops computing the expression as soon as the result
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd