1.2 SQL Introduction | Define Tuple, field, relation | what is
query, clause | Popular RDBMS
Welcome to SQL Command Notes!
SQL Terminologies
Tables
In SQL, data is organized into tables which consist of columns and
rows. Each column represents a field, and each row represents a
record.
Relations
QL is a relational database management system. A relation is a table
S
in which every row has a unique identity, and the rows (tuples) within a
table are unordered.
Tuples
tuple is a row in a table. It is composed of a set of fields/columns
A
that represent a single record.
Fields
In a table, each column represents a field. A field contains the same
type of data for every tuple in the table.
SQL Commands
Types
● D DL (Data Definition Language) - used to create, delete, and
modify database objects
● DML (Data Manipulation Language) - used to retrieve, insert,
delete, and modify data in the tables
, ● D CL (Data Control Language) - used to manage user access
permissions to the database and its objects
● TCL (Transaction Control Language) - used to manage
transactions, such as committing or rolling back changes
Query
QL queries are used to retrieve data from tables. The SELECT
S
statement is used to identify the data to be retrieved, and WHERE
clause is used to filter the data.
Classes
here are several SQL commands that fall into specific classes. Some
T
of these classes include:
● DL commands: CREATE, ALTER, DROP
D
● DML commands: INSERT, UPDATE, DELETE
● DCL commands: GRANT, REVOKE
● TCL commands: COMMIT, ROLLBACK
Understanding Relational Databases and Vendors
elational databases are an efficient way to store and manage data.
R
They offer features such as data integrity, scalability, and security.
Some popular relational database vendors include Oracle, Microsoft
SQL Server, MySQL, and PostgreSQL.
query, clause | Popular RDBMS
Welcome to SQL Command Notes!
SQL Terminologies
Tables
In SQL, data is organized into tables which consist of columns and
rows. Each column represents a field, and each row represents a
record.
Relations
QL is a relational database management system. A relation is a table
S
in which every row has a unique identity, and the rows (tuples) within a
table are unordered.
Tuples
tuple is a row in a table. It is composed of a set of fields/columns
A
that represent a single record.
Fields
In a table, each column represents a field. A field contains the same
type of data for every tuple in the table.
SQL Commands
Types
● D DL (Data Definition Language) - used to create, delete, and
modify database objects
● DML (Data Manipulation Language) - used to retrieve, insert,
delete, and modify data in the tables
, ● D CL (Data Control Language) - used to manage user access
permissions to the database and its objects
● TCL (Transaction Control Language) - used to manage
transactions, such as committing or rolling back changes
Query
QL queries are used to retrieve data from tables. The SELECT
S
statement is used to identify the data to be retrieved, and WHERE
clause is used to filter the data.
Classes
here are several SQL commands that fall into specific classes. Some
T
of these classes include:
● DL commands: CREATE, ALTER, DROP
D
● DML commands: INSERT, UPDATE, DELETE
● DCL commands: GRANT, REVOKE
● TCL commands: COMMIT, ROLLBACK
Understanding Relational Databases and Vendors
elational databases are an efficient way to store and manage data.
R
They offer features such as data integrity, scalability, and security.
Some popular relational database vendors include Oracle, Microsoft
SQL Server, MySQL, and PostgreSQL.
