SELECT Statement Comprehension

Sorting operation(s) should be placed after filter statement(s)

To understand this syntax, we may think about how a query is executed. When sorting a huge amount of data, our data base has much more burden, it will take more time to return the final result especially when the table we are retrieving contains a very large amount of data. So filtering those data before we sorting them is time efficient and performance efficient.

SELECT * FROM [table]
WHERE [expression]
ORDER BY [column|expression]

Filtering statement(s) and Sorting statement(s) are OPTIONAL

SELECT 1, 2, 3; -- this is valid even

Can write expression when selecting columns

SELECT [column1], [column2], [column3], [expression]
FROM [table]

Let a table having a column named count which is a integer. Then, we can write this

SELECT count + 1
FROM [table]

The query result will display a column that every element was added by 1.

Alias of a table

SELECT count + 1 AS new_count;
SELECT count + 1 AS "new count";
SELECT count + 1 AS `new count`; -- only MySQL supports this syntax

• Use _ to separate words OR close the string of alias name with ".
• If using MySQL, `new count` is also available to set alias name.

SELECT [column]|>[expr|func] AS [new_column_name];