WHERE

Used to filter records. It is used to extract only those records that fulfill a specified condition. ex. : WHERE Country = 'Mexico'

GROUP BY

Groups rows that have the same values into summary rows, like "find the number of customers in each country". It's is often used with aggregate functions (COUNT(), MAX(), MIN(), SUM(), AVG()) to group the result-set by one or more columns.

ORDER BY

Used to sort the result-set in ascending or descending order. To sort the records in descending order, use the DESC keyword. ex. : ORDER BY Country DESC

HAVING

Added to SQL because the WHERE keyword cannot be used with aggregate functions.

Conditions

• The AND operator displays a record if all the conditions separated by AND are TRUE
• The OR operator displays a record if any of the conditions separated by OR is TRUE
• The NOT operator displays a record if the condition(s) is NOT TRUE
• The IN operator allows you to specify multiple values in a WHERE clause
• The BETWEEN operator selects values within a given range. The values can be numbers, text, or dates

Operators

• The IIF() function returns true or false according to a condition
• The COUNT() function returns the number of rows that matches a specified criterion
• The AVG() function returns the average value of a numeric column
• The SUM() function returns the total sum of a numeric column
• The MIN() function returns the smallest value of the selected column
• The MAX() function returns the largest value of the selected column