Database systems administration traning 02
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This document covers database concepts including select operations, projection, arithmetic operators, operator precedence, null values, column aliases, and assignment questions involving queries. It discusses selecting specific and multiple columns, using arithmetic operators like addition and subtraction, enforcing operator precedence with parentheses, how null values are treated in expressions, and renaming columns with aliases. It provides examples of queries to display concatenated name and job, filter employees by department number, and select name and salary by job title.
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Database systems administration traning 02
- 4. Projection (Selecting Multiple Columns ..Cont.)
- 5. Projection (Selecting Multiple Columns ..Cont.)
- 6. Projection with Selection using WHERE Clause
- 7. Arithmetic Operators Operator Description + Add - Subtract * Multiply / Divide
- 9. Operator Precedence * / + - • Multiply and division take priority over addition and subtraction • Operators of the same priority are evaluated from left to right. • Parentheses are used to force prioritized evaluation.
- 10. Operator Precedence Notice that multiplication is performed before addition
- 11. Using Parentheses You can enforce the rules of precedence by using the parenthesis
- 12. Null Values NULL Value: • Unavailable Value • Unassigned Value • Unknown Value • Inapplicable Value Null Value
- 13. Null Values in Arithmetic Expression Arithmetic expression containing a Null Value evaluates to null
- 14. Column Aliases • Renames a column heading • Aliases immediately follows column names. • Optional AS keyword between column name and aliases. • Requires double quotation marks if it contains spaces or special characters or is case sensitive
- 16. Assignment 02 1. Display the name concatenated with the job, separated by comma and space also name the column with Employee and Title. 2. Display the name and job of the employee , they belongs to department number 20. 3. Display the name and salary of the person whose job title is MANAGER.