SQL (Structured Query Language) is a special-purpose programming language designed for managing data held in a relational database management system (RDBMS). Originally based upon relational algebra and tuple relational calculus, SQL consists of a data definition language and a data manipulation language. The scope of SQL includes data insert, query, update and delete, schema creation and modification, and data access control.
The Data Definition Language (DDL) is used to manage table and index structure. CREATE, ALTER, RENAME, DROP and TRUNCATE statements are the names of few data definition elements.
LIKE is a keyword that is used in the WHERE clause. Basically, LIKE allows us to do a search based operation on a pattern rather than specifying exactly what is desired (as in IN) or spell out a range (as in BETWEEN).
The syntax is as follows: SELECT "column_name" FROM "table_name" WHERE "column_name" LIKE {PATTERN}
{PATTERN} often consists of wildcards. In SQL, there are two wildcards:
1=% (percent sign) represents zero, one, or more characters.
2=_ (underscore) represents exactly one character.
RENAME: - With RENAME statement you can rename a table. REVOKE: - The REVOKE command removes user access rights or privileges to the database objects. GRANT: - In SQL GRANT is a command used to provide access or privileges on the database objects to the users. UPDATE: - The UPDATE Statement is used to modify the existing rows in a table.
RENAME, REVOKE and GRANT are DDL(Data Definition Language) commands and UPDATE is DML(Data Manipulation Language) command.
The SELECT keyword allows us to grab all information from a column (or columns) on a table. This, of course, necessarily means that there will be redundancies. What if we only want to select each distinct element? This is easy way to accomplish in SQL. All we need to do is that to add DISTINCT after SELECT. The syntax is as follows:
Sometimes we need to change the data type of a column. To do this, we use the ALTER TABLE Modify Column command. Sytax: ALTER TABLE table_name MODIFY column_name "New Data Type"
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