I.M MIDTERMS | WEEK 9 - 11

Aggregate Functions

These are functions that can be used in a group of rows to give result of a single value.

Aggregate Functions

An example of this function is MIN(), MAX(), COUNT(), SUM(), AND AVG()

MIN()

This function is used if you want to get the lowest row value of the chosen column

MAX()

This is used if you want to get the highest row value of the chosen column

COUNT()

This function is used if you want to get the number of rows in the selected column

SUM()

This function is used to get the summation of all rows selected numeric column

AVG()

This function is used to get the average of all rows of selected numeric column

Limit Clause

This is used to specify the number of retrieved data rows. It is useful on large tables with more than thousands of rows as retrieving many data will generate poor performance specially when it is not needed.

LIKE Operator

This is used in a WHERE clause to retrieve a specific string pattern.

Wildcard Characters

To produce a string pattern, __ are frequently used to signify omitted characters.

%(Percent)

This symbol is used to signify zero to multiple characters in the result

_ (Underscore)

This symbol is used to signify one or single characters in the result

Aliases

This is used to give a table or column a temporary name

Aliases

These only exists during the query duration, frequently used to make the name of the table or column more readable.

Order By Clause

This clause is used if you want to sort the data rows result based on specified columns, it can be ascending or descending.

Group By Clause

This clause will aggregate or combine data rows together that have the same values. It will collect all the values of data rows with similar type and display it by showing different types that’s collected.

Group by Clause

This clause is like answering the question “how many employees in each branch”

Having Clause

This clause is used to filter result data rows on a Group By Clause.

MySQL Union Operator

This operator will unite the query result of more than one SELECT statements and will remove duplicate results.