SQL is followed by unique set of rules and guidelines called Syntax. This tutorial gives you a quick start with SQL by listing all the basic SQL Syntax:
All the SQL statements start with any of the keywords like SELECT, INSERT, UPDATE, DELETE, ALTER, DROP, CREATE, USE, SHOW and all the statements end with a semicolon (;).
Important point to be noted is that SQL is case insensitive, which means SELECT and select have same meaning in SQL statements, but MySQL makes difference in table names. So if you are working with MySQL, then you need to give table names as they exist in the database.
SQL SELECT Statement:
SELECT column1, column2....columnN FROM table_name;
SQL DISTINCT Clause:
SELECT DISTINCT column1, column2....columnN FROM table_name;
SQL WHERE Clause:
SELECT column1, column2....columnN FROM table_name WHERE CONDITION;
SQL AND/OR Clause:
SELECT column1, column2....columnN FROM table_name WHERE CONDITION-1 {AND|OR} CONDITION-2;
SQL IN Clause:
SELECT column1, column2....columnN FROM table_name WHERE column_name IN (val-1, val-2,...val-N);
SQL BETWEEN Clause:
SELECT column1, column2....columnN FROM table_name WHERE column_name BETWEEN val-1 AND val-2;
SQL LIKE Clause:
SELECT column1, column2....columnN FROM table_name WHERE column_name LIKE { PATTERN };
SQL ORDER BY Clause:
SELECT column1, column2....columnN FROM table_name WHERE CONDITION ORDER BY column_name {ASC|DESC};
SQL GROUP BY Clause:
SELECT SUM(column_name) FROM table_name WHERE CONDITION GROUP BY column_name;
SQL COUNT Clause:
SELECT COUNT(column_name) FROM table_name WHERE CONDITION;
SQL HAVING Clause:
SELECT SUM(column_name) FROM table_name WHERE CONDITION GROUP BY column_name HAVING (arithematic function condition);
SQL CREATE TABLE Statement:
CREATE TABLE table_name( column1 datatype, column2 datatype, column3 datatype, ..... columnN datatype, PRIMARY KEY( one or more columns ) );
SQL DROP TABLE Statement:
DROP TABLE table_name;
SQL CREATE INDEX Statement :
CREATE UNIQUE INDEX index_name ON table_name ( column1, column2,...columnN);
SQL DROP INDEX Statement :
ALTER TABLE table_name DROP INDEX index_name;
SQL DESC Statement :
DESC table_name;
SQL TRUNCATE TABLE Statement:
TRUNCATE TABLE table_name;
SQL ALTER TABLE Statement:
ALTER TABLE table_name {ADD|DROP|MODIFY} column_name {data_ype};
SQL ALTER TABLE Statement (Rename) :
ALTER TABLE table_name RENAME TO new_table_name;
SQL INSERT INTO Statement:
INSERT INTO table_name( column1, column2....columnN) VALUES ( value1, value2....valueN);
SQL UPDATE Statement:
UPDATE table_name SET column1 = value1, column2 = value2....columnN=valueN [ WHERE CONDITION ];
SQL DELETE Statement:
DELETE FROM table_name WHERE {CONDITION};
SQL CREATE DATABASE Statement:
CREATE DATABASE database_name;
SQL DROP DATABASE Statement:
DROP DATABASE database_name;
SQL USE Statement:
USE DATABASE database_name;
SQL COMMIT Statement:
COMMIT;
SQL ROLLBACK Statement:
ROLLBACK;
Creating a basic table involves naming the table and defining its columns and each column's data type.
The SQL CREATE TABLE statement is used to create a new table.
Syntax:
Basic syntax of CREATE TABLE statement is as follows:
CREATE TABLE table_name( column1 datatype, column2 datatype, column3 datatype, ..... columnN datatype, PRIMARY KEY( one or more columns ) );
CREATE TABLE is the keyword telling the database system what you want to do. In this case, you want to create a new table. The unique name or identifier for the table follows the CREATE TABLE statement.
Then in brackets comes the list defining each column in the table and what sort of data type it is. The syntax becomes clearer with an example below.
A copy of an existing table can be created using a combination of the CREATE TABLE statement and the SELECT statement. You can check complete details at Create Table Using another Table.
Example:
Following is an example, which creates a CUSTOMERS table with ID as primary key and NOT NULL are the constraints showing that these fields can not be NULL while creating records in this table:
SQL> CREATE TABLE CUSTOMERS( ID INT NOT NULL, NAME VARCHAR (20) NOT NULL, AGE INT NOT NULL, ADDRESS CHAR (25) , SALARY DECIMAL (18, 2), PRIMARY KEY (ID) );
You can verify if your table has been created successfully by looking at the message displayed by the SQL server, otherwise you can use DESC command as follows:
SQL> DESC CUSTOMERS; +---------+---------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------+---------------+------+-----+---------+-------+ | ID | int(11) | NO | PRI | | | | NAME | varchar(20) | NO | | | | | AGE | int(11) | NO | | | | | ADDRESS | char(25) | YES | | NULL | | | SALARY | decimal(18,2) | YES | | NULL | | +---------+---------------+------+-----+---------+-------+ 5 rows in set (0.00 sec)
Now, you have CUSTOMERS table available in your database which you can use to store required information related to customers.
