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Database Management Systems Lecture Notes
A 'College Degree' attribute for a person.i.e, one person may not have a college degree, another person may have one and a third person may have 2 or more degrees. A multi-valued attribute may have lower and upper bounds on the number of values allowed for each individual entity.


Having null values for the primary key implies that we cannot identify some tuples. A special select list consisting of a single '*' requests all columns in all tables in the FROM clause. Since two null columns may eventually be assigned different values, one null can't be compared to another in the...


NOT NULL – It specifies that column is mandatory. This feature allows you to prevent data from being entered into table without certain columns having data in them. First_name Sachin Rahul Ajay Sunil Kapil Anil. To select all columns in the table you can use select * from table_name


064-29: Creating Efficient SQL - Union Join without the Union Clause
select aNumCol from a UNION select aCharCol from b. Alot more subtle and, worse yet, platform specific is the issue of database performance. Since each member of a UNION clause is itself a fully formed, stand alone fullselect statement, database implementations execute each member...


Nulls in SQL
Is the phone number unlisted? Database solution: null values. Queries with NULL. The WHERE condition for tuples in a query answer must evaluate to TRUE / 1. Queries with NULL have weird 'logic'. • SELECT e.name FROM Emp e WHERE (e.age>20 OR e.age<=20) -- is this always true?


The OWASP Foundation
1'))) UNION ALL SELECT NULL, Concatenated SQL query# AND ((('RaNd' LIKE 'RaNd. The number of columns in the SELECT statement is fewer than the number of columns that you want to inject. Front Range OWASP Conference, Denver (USA).


Egitim-Introduction to Oracle 9i SQL Student Guide Vol2.pdf
Group functions ignore null values. If you want to include null values, use the NVL function. SELECT last_name,department_id,TO_CHAR(null) FROM employees UNION SELECT TO_CHAR(null),department_id,department_name FROM departments


SQL - unions clause
The SQL UNION clause/operator is used to combine the results of two or more SELECT statements without returning any duplicate rows. To use UNION, each SELECT must have the same number of columns selected, the same number of column expressions, the same data type...


Using the Set Operators Questions
When used with two SELECT statements, the UNION set operator returns the results of both queries.However,if there are any duplicates, they are A. It returns rows from the combined queries along with NULL values B. It returns rows for the combined queries after eliminating duplicates C. It...


Google Colab
You can do so by selecting the cell that you want to move and clicking the UP CELL or DOWN CELL buttons shown in the following screenshot Colab allows you to save your work to your Google Drive. To save your notebook, select the following menu options