SQL (Structured Query Language) syntax refers to the set of rules and conventions used to write and execute queries in SQL, which is a domain-specific language designed for managing relational databases. SQL syntax consists of various keywords, operators, functions, and clauses that are used to manipulate data stored in a database.
Here are some common elements of SQL syntax:
- SELECT: Used to retrieve data from one or more tables in a database.
- FROM: Specifies the table(s) from which to retrieve data.
- WHERE: Specifies conditions that data must meet to be included in the result set.
- JOIN: Combines data from two or more tables based on a related column between them.
- ORDER BY: Sorts the result set based on one or more columns.
- GROUP BY: Groups rows in the result set based on one or more columns.
- INSERT INTO: Adds new data into a table.
- UPDATE: Modifies existing data in a table.
- DELETE: Removes data from a table.
- AND, OR, NOT: Logical operators used in combination with conditions in WHERE clauses.
- COUNT, SUM, AVG, MAX, MIN: Aggregate functions used to perform calculations on groups of rows.
Here’s an example of SQL syntax for a basic SELECT statement, which is used to retrieve data from a database:
SELECT column1, column2, ... FROM table_name WHERE condition;
Let’s break down the syntax:
SELECT: This is the SQL keyword used to specify the columns or data that you want to retrieve from the database.
column1, column2, ...: These are the names of the columns that you want to select. You can specify multiple columns separated by commas.
FROM: This is the SQL keyword used to specify the table from which you want to retrieve data.
table_name: This is the name of the table from which you want to select data.
WHERE: This is the SQL keyword used to specify the condition or criteria that the retrieved data must meet in order to be included in the result set.
condition: This is the condition or criteria that you want to apply to filter the data. It can include comparisons, logical operators, and other SQL operators.
Here’s an example of a complete SELECT statement with SQL syntax and example data:
SELECT first_name, last_name, age FROM users WHERE age > 18;
In this example, the SELECT statement is retrieving the
age columns from the
users table, but only for rows where the value of the
age column is greater than 18.
SQL syntax may vary slightly depending on the specific database management system (DBMS) being used, such as MySQL, PostgreSQL, Oracle, or Microsoft SQL Server. It’s important to refer to the documentation of the specific DBMS being used for the exact syntax rules and conventions.