SQL
Structured Query Language
Last updated
Was this helpful?
Structured Query Language
Last updated
Was this helpful?
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.
MySQL
Access
Oracle
Microsoft SQL Server
Postgres
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.
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.
It is common and best practice to capitalize all SQL commands, like SELECT and FROM, and keep everything else in your query lower case.
