SQL

Structured Query Language

An entity-relationship diagram (ERD) is a common way to view how data is structured in a database.

Structured Query Language (SQL) is a language that allows us to access data stored in a database.

Types of SQL Databases

SELECT: This clause specifies the columns from the data source that should be included in the query results.
FROM: This clause specifies the data source(s) that should be queried. This can be a table, a view, or the results of another query.
WHERE: This clause specifies conditions that must be met for a row to be included in the query results.
GROUP BY: This clause groups the rows of the query results by the values in one or more columns, allowing aggregate functions to be applied to each group.
HAVING: This clause is used to filter the groups in the query results, based on the values of aggregate functions applied to each group.
ORDER BY: This clause specifies the order in which the rows of the query results should be returned.
LIMIT: This clause limits the rows returned.

Order Clause Function

Order	Clause	Function
1	`FROM`	Tables are joined to get the base data.
2	`WHERE`	The base data is filtered.
3	`GROUP BY`	The filtered base data is grouped.
4	`HAVING`	The grouped base data is filtered.
5	`SELECT`	The final data is returned.
6	`ORDER BY`	The final data is sorted.
7	`LIMIT`	The returned data is limited to row count.

FROM

Tables are joined to get the base data.

WHERE

The base data is filtered.

GROUP BY

The filtered base data is grouped.

HAVING

The grouped base data is filtered.

SELECT

The final data is returned.

ORDER BY

The final data is sorted.