SQL stands for Structured Query Language is a database computer language used for managing data when used with application in a Relational Database Management System (RDBMS).
There are many database software available which used the same query language. Some of them are Oracle, My SQL, DB2 etc.
As the name suggest Structures Query language so it uses QUERY for retrieval of data from the database, and that query has a structure which is same for all databases software.
SQL has statements, which are used as query :
Query
|
Used For
|
Select
|
Data Retrieval
|
Insert
Update
Delete
Merge
|
Data Manipulation Language (DML)
|
Create
Alter
Drop
Renance
Truncate
|
Data Definition Language (DDL)
|
Commit
Rollback
Savepoint
|
Transaction Control
|
Grant
Revoke
|
Data Control Language (DCL)
|
Select Statement :
SELECT *|{[DISTINCT] column|expression [alias],...} FROM table;
1. SELECT identifies what columns
2. FROM identifies which table
In SQL you can also perform Arithmetic Operations, but we have to keep in mind the operator are executed that is the OPERATOR PRECEDENCE :
1. * (multiplication)
2. / (division)
3. + (addition)
4. - (subtraction)
Like programming languages here also we can do CONCATENATION, by using the concatenation operator ie '||'
Ex.
SELECT last_name||job_id AS "Employees" FROM employees;
Now for retrieving of data we can also use a where condition, which helps us to make our search more accurate.
SYNTAX :
SELECT *|{[DISTINCT] column|expression [alias],...}
FROM table
[WHERE condition(s)];
FROM table
[WHERE condition(s)];
*The WHERE clause follows the FROM clause.
Ex.
SELECT employee_id, last_name, job_id, department_id
FROM employees
WHERE department_id = 90 ;
These are some of the basic operations that you can perform for retrieval of data from the database using condition if you want to.
