SQL commands can be classified in to three types: Data Definition Language commands (DDL) Data Manipulation Language commands (DML) Data Control Language commands (DCL) DDL commands are used to define a database, including creating, altering, and dropping tables and establishing constraints. DML commands are used to maintain and query a database, including updating, inserting, modifying, and querying data. DCL commands are used to control a database including administering privileges and saving of data | Structured Query Language Introduction SQL stands for “Structured Query Language.” SQL is a language used to interact with the database. SQL is a data access language. SQL is based on relational tuple calculus. SQL is a standard relational database management language. SQL commands consist of English-like statements which are used to query, insert, update, and delete data. SQL is referred to as nonprocedural database language. Commands in SQL SQL commands can be classified in to three types: Data Definition Language commands (DDL) Data Manipulation Language commands (DML) Data Control Language commands (DCL) DDL commands are used to define a database, including creating, altering, and dropping tables and establishing constraints. DML commands are used to maintain and query a database, including updating, inserting, modifying, and querying data. DCL commands are used to control a database including administering privileges and saving of data. Datatypes in SQL In relational model the . | Structured Query Language Introduction SQL stands for “Structured Query Language.” SQL is a language used to interact with the database. SQL is a data access language. SQL is based on relational tuple calculus. SQL is a standard relational database management language. SQL commands consist of English-like statements which are used to query, insert, update, and delete data. SQL is referred to as nonprocedural database language. Commands in SQL SQL commands can be classified in to three types: Data Definition Language commands (DDL) Data Manipulation Language commands (DML) Data Control Language commands (DCL) DDL commands are used to define a database, including creating, altering, and dropping tables and establishing constraints. DML commands are used to maintain and query a database, including updating, inserting, modifying, and querying data. DCL commands are used to control a database including administering privileges and saving of data. Datatypes in SQL In relational model the data are stored in the form of tables. A table is composed of rows and we create a table we must specify a datatype for each of its columns. These datatypes define the domain of values that each column can take. Datatypes: built-in user-defined types Some of the built-in datatypes are string datatype to store characters, number datatype to store numerical value, and date and time datatype to store when the event happened (history, date of birth, etc.). Datatypes in SQL Char CHAR datatype to store fixed-length character data. Maximum size = 2000 bytes Varchar Varchar datatype to store variable-length character data. Number Number types let you store numeric data (integers, real numbers, and floating-point numbers), represent quantities, and do calculations. Datatypes in SQL NChar To store multi byte fixed length character data. Its same as Char only difference is it is used to store characters of different language like Japenese , chinese etc. Number of characters it can store .
