SQL is a language used to interact with data in a database

SQL or Structured Query Language lets you create, read, update and delete data in a database. You write queries against your database in SQL.

Different DBMSs have slightly different dialects of SQL, but there’s a lot of commonality.

Usually use "" around your SQL identifiers - table and column names. It isn’t always required, but is useful. Use '' around SQL strings, so it is easy to tell them apart. This is just convention, but it helps. Likewise, use ALLCAPS for SQL keywords like SELECT, FROM and stuff.

• SELECT gets data from rows in a table, LIMIT limits the number of rows returned.
• WHERE only returns rows that match a condition.
• NULL represents missing data.
• ORDER BY sorts query results.
• Aggregate functions return statistics about groups of rows
• a subquery is a SQL query inside another, JOIN connects tables