SQL Query Writing (PART V)
In this article we are going to learn about some SQL queries.
- Structured Query Language(SQL) is database language by using this we can perform certain operations on the existing database.
- A query is used to request for data in to a database.
- In SQL queries can be categorized as-
- DDL — Data Definition Language
- DML — Data Manipulation Language
SELECT Statement:
- Select Statement can be used to retrieve record from the database.
- If we can to show all records from the table then * sign can be used.
SELECT ALL RECORDS:
Consider Following table tblTeacher
Syntax:
SELECT * FROM TABLE_NAME
Example:
SELECT * FROM tblTeacher
SELECT WITH WHERE CLAUSE:
- From this above table if we want to select only specific table then where clause can be used.
Syntax:
SELECT * FROM TABLE_NAME
WHERE condition
Example:
- If we want to retrieve only the TeacherID,FirstName then query like-
SELECT TeacherID,FirstName
FROM tblTeacher
WHERE TeacherID=1002
SELECT WITH NUMERIC AND STRING:
NUMERIC:
- If we want to retrieve the information from the table by using any numeric value then equal to sign(=) can be used.
Example:
STRING:
- If we want to retrieve the information from the table by using any string value then equal to sign(=) then single quote(‘’) can be used.
Example:
SELECT WITH WILDCARD:
- If we want to search any record with a specific pattern then LIKE operator is used in a WHERE clause to search for a specified pattern in a column.
There are two wildcards often used with the LIKE operator:
- %=The percent sign represents zero, one, or multiple characters
- _=The underscore represents a single character
Syntax:
SELECT COLUMN_NAME(S)
FROM TABLE_NAME
WHERE COLUMN_NAME LIKE ‘%ABC%’
Example 1:
Example 2:If we can to display only those records whose Subject name ends with ‘lar’ then query like-
Example 3:Finds any values that have S in 1st position and L in 3rd position.
Example 4:Finds any values that have A in 1st position and are at least 4 characters in length.
SPECIFIC COLUMN WITH ALIAS:
- It can be used to give a temporary name to the column.
- And it only exists for the duration of the query
Syntax:
SELECT COLUMN_NAME AS NEW_COL_NAME
FROM TABLE_NAME
Example:
SELECT Salary AS Payment
FROM tblTeacher
SELECT WITH INNER JOIN:
- When we do inner join,It can returns only those records which have
matching values in both the table.
Syantax:
SELECT COLUM_NAME(S)
FROM TABLE1
INNER JOIN TABLE2 ON
TABLE1.COLUMN_NAME=TABLE2.COLUMN_NAME;
Example:
SELECT WITH LEFT JOIN:
When we do left join,it can show all records from the left side of table and only matching records in right side of table.
Syntax:
SELECT COLUM_NAME(S)
FROM TABLE1
LEFT JOIN TABLE2 ON
TABLE1.COLUMN_NAME=TABLE2.COLUMN_NAME;
Example:
SELECT WITH RIGHTJOIN:
When we do right join,it can show all records from the right side of table and only matching records in left side of table.
Syntax:
SELECT COLUM_NAME(S)
FROM TABLE1
RIGHT JOIN TABLE2 ON
TABLE1.COLUMN_NAME=TABLE2.COLUMN_NAME;
Example:
To understand more about SQL Queries must watch following video.It’s really help you…….
Thank You…..!!!
