Structured Query Language (SQL)

Structured query language(SQL) is a non-procedural computer language, aimed to Store, manipulate and query data stored in relational database and also used to create interface between user and database. Now-a-days Structured query language(SQL) is mostly used in web servers to store data.

Advantages of Structured query language(SQL) :

1. High speed

2. Easy to learn and understand

3. No coding required

4. Emergence of RDBMS

5. SQL is Portable

Structured query language(SQL) statements:

Structured query language(SQL) command or statement is a special kind of sentence that contain clauses and all end with a semicolon(;) just as a sequence end with a period.

Structured query language(SQL) statements are divided into four sub languages:

1. Data definition language (DDL): It is used to define the structure of tables in the database.

2. Data manipulation language (DML): It is used to the manipulate the data in the database.

3.Data Control Language (DCL): It is used to control data stored in the database.

4.Transaction Control Language (TCL): It is used to control the transactions in the database.

We are going to discuss about data definition language and data manipulation language:

Data definition language (DDL)

CREATE TABLE COMMAND

CREATE TABLE <table name> (<attribute_name> <datatype> (size) (constraint), <attribute_name> <datatype> (size) (constraint), <attribute_name> <datatype> (size) (constraint), <attribute_name> <datatype> (size) (constraint),.......);

ALTER TABLE COMMAND

1.ADD COLUMN

ALTER TABLE <table_name> ADD <column_name> <data_type>;

2.DROP COLUMN

ALTER TABLE <table_name> DROP COLUMN <column_name>;

3.MODIFY COLUMN DATA TYPE

ALTER TABLE <table_name> MODIFY <column_name> <new_data_type>;

4.DELETE CONSTRAINT

ALTER TABLE <table_name> DROP <constraint_name>; OR
ALTER TABLE <table_name> MODIFY <column_name> <data_type> <new_constraint_name>;

5.RENAME COLUMN

ALTER TABLE <table_name> RENAME COLUMN <old_name> TO <new_name>; OR
ALTER TABLE <table_name> CHANGE COLUMN <old_name> <new_name> <data_type>;

DROP TABLE COMMAND

DROP TABLE <table_name>;

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Data manipulation language (DML)

1.INSERT COMMAND

INSERT INTO <table_name> VALUES (<value_1>,<value_1>,<value_2>,<value_3>....); OR
INSERT INTO <table_name> (<col_name_1>,<col_name_2>,<col_name_3>....) VALUES (<value_1>,<value_1>,<value_2>,<value_3>....);

2.DELETE COMMAND

DELETE FROM <table_name> WHERE <column_name>=<some_value>;

3.SELECT COMMAND

SELECT <attribute_name_1>,<attribute_name_2>... FROM <table_name>;
SELECT* FROM <table_name>; // FOR SELECTING ALL THE VALUES

4.DISTINCT KEYWORD

SELECT DISTINCT <attribute_name> FROM <table_name>;

5.WHERE CLAUSE

SELECT <attribute_name> FROM <table_name> WHERE <attribute_name>=VALUE;

6.UPDATE COMMAND

UPDATE <table_name> SET COLUMN_1=VALUE_1 WHERE COLUMN_2=VALUE;

7.ORDER BY CLAUSE

SELECT <attribute_name> FROM <table_name> WHERE <attribute_name><VALUES ORDER BY <attribute_name>;

8.GROUP BY CLAUSE

SELECT <attribute_name> FROM <table_name> GROUP BY <attribute_name>;

9.HAVING CLAUSE

SELECT <attribute_name> FROM <table_name> GROUP BY <attribute_name> HAVING <condition>;

OPERATORS IN STRUCTURED QUERY LANGUAGE(SQL)

1.NULL OPERATOR

SELECT <attribute_name> FROM <table_name> WHERE <attribute_name>=NULL;

2.LIKE OPERATOR

SELECT <attribute_name> FROM <table_name> WHERE <attribute_name> LIKE "S%"; OR
SELECT <attribute_name> FROM <table_name> WHERE <attribute_name> LIKE "S____";

3.BETWEEN OPERATOR

SELECT <attribute_name> FROM <table_name> WHERE <attribute_name> BETWEEN 0 AND 45;

4.AND OPERATOR

SELECT <attribute_name> FROM <table_name> WHERE <attribute_name>=RAM AND <attribute_name>=SHAM;

5.OR OPERATOR

SELECT <attribute_name> FROM <table_name> WHERE <attribute_name>=RAM OR <attribute_name>=SHAM;

6. IN OPERATOR

SELECT <attribute_name> FROM <table_name> WHERE <attribute_name> IN ('A','B');

7.NOT WITH IN OPERATOR

SELECT <attribute_name> FROM <table_name> WHERE <attribute_name> NOT IN ('A','B');

GROUP FUNCTION IN STRUCTURED QUERY LANGUAGE(SQL)

1.AVG FUNCTION

SELECT AVG(attribute_name) FROM <table_name>;

2.MAX FUNCTION

SELECT MAX(attribute_name) FROM <table_name>;

3.MIN FUNCTION

SELECT MIN(attribute_name) FROM <table_name>;

4.SUM FUNCTION

SELECT SUM(attribute_name) FROM <table_name>;

5.COUNT FUNCTION

SELECT COUNT(attribute_name) FROM <table_name>;

CARTESIAN PRODUCT IN STRUCTURED QUERY LANGUAGE(SQL)

SELECT* FROM <table_1> CROSS JOIN <table_2>; OR 
SELECT* FROM <table_1>,<table_2>;

UNION IN STRUCTURED QUERY LANGUAGE(SQL)

SELECT <attribute_name> FROM <table_1>,<table_2> WHERE <condition> UNION SELECT <attribute_name> FROM <table_1>,<table_2> WHERE <condition>;

This is all about the DDL and DML commands in Structured query language(SQL). But keep that in mind that without practice just reading them is just waste of time. So, practice them properly. For proper tutorial check this you tube tutorial.

Video:https://youtu.be/I2W-tX85dnk

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