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Sql Query Examples
04.03.2025 12:47 197 Displayed

Sql Query Examples

Customer’s

name

surname

Date of birth

city

gender

point

1

Ahmet

Cansever

1956-02-19 00:00:00.000

İstanbul

M

64

2

Mehmet

Aydın

1976-02-19 00:00:00.000

Samsun

M

55

3

Aliye

Seven

1966-06-10 00:00:00.000

Konya

F

45

4

Burak

Sayın

1996-02-19 00:00:00.000

İstanbul

M

23

5

Beyza

Kılıç

1955-12-30 00:00:00.000

Manisa

F

85

 

The information in the table above should be translated into English (For example, Genetics, Name and Surname) and information should be changed according to UK-US

 SQL SELECT

To list the name and surname columns in the customer table;

 

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Select name, surname FROM customer

To list all records in the customer table;

 

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Select *From customer

SQL SELECT DISTINCT

A column in a table may contain duplicate values. We can list distinct values ​​with Distinct.

 

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SELECT DISTINCT city FROM customer;

SQL WHERE

With the Where keyword, we can ensure that only records that meet the specified rule are listed. For example, to list records in the customer table whose city column is Istanbul;

 

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SELECT * FROM customer WHERE city='istanbul'

or to list records with gender "F";

 

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SELECT * FROM customer WHERE gender='K'

Operators we can use with Where:

Operator

Explanation

=

Equal

<> 

Not Equal. Note: In some versions “!=” can be used.

> 

Greater

< 

Smaller .

>=

Greater Equal

<=

Smaller Equal

BETWEEN

between

LIKE

Pattern search

IN

To specify multiple possible values ​​for a column

SQL AND – OR Usage

AND Operator works if Condition 1 and Condition 2 are true. For example, to list those whose Gender is "E" and City is "Istanbul" in the customer table;

 

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SELECT * FROM customer

WHERE city='İstanbul'

AND gender='E'

OR operator works if either Condition 1 or Condition 2 is true. For example, to list the cities Istanbul or Samsun in the customer table;

 

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SELECT * FROM customer

WHERE city='İstanbul'

OR city='Samsun'

AND and OR operators can also be used together. For example, to list the customers table with gender 'K' and city 'Konya' or 'Manisa'.

 

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SELECT * FROM customer

WHERE gender='K'

AND (City='Konya' OR City='Manisa')

SQL Where usage ile ilgili daha fazla örnek için tıklayın.

Click for more examples of using SQL Where.

SQL ORDER BY USAGE

ORDER BY sorts records in ascending order by default. You can use the DESC keyword to sort records in descending order. For example, let's sort records in the customer table by the name column in ascending and descending order.

 

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SELECT * FROM customer

ORDER BY ad

Descending sort example;

 

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SELECT * FROM customer

ORDER BY ad DESC

INSERT INTO USAGE

It is used to add a record. For example, let's add a record to the customer table.

 

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INSERT INTO customer(ad, surname, date of birth, city, gender, point)

VALUES ('Ali','Şahin','2000-10-12','Burdur','E',68)

SQL UPDATE USAGE

It is used to make changes and updates on records. For example, let's change the point of the record with customerno 3 to 90.

 

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UPDATE customers

SET point=90

WHERE customer no=3

SQL DELETE USAGE

It is used to delete a record from the table. For example, to delete a record with customer no 4

 

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DELETE FROM customers

WHERE customer no=4

To delete all records from the customers table

 

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DELETE * FROM customers

SQL SELECT TOP USAGE

It is used to display a specified number of records. For example, let's list the first 5 records in the customers table.

 

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SELECT TOP 5 * FROM customers

SQL LIKE USAGE

It is used to search for a specified value. For example, let's list the records in the customers table whose city starts with S.

 

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SELECT * FROM customers

WHERE city LIKE 's%'

To list records whose city ends with s;

 

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SELECT * FROM customers

WHERE city LIKE '%s'

To list the records that contain "tan" in the city;

 

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SELECT * FROM customers

WHERE city LIKE '%tan%'

SQL PLACEHOLDER CHARACTERS

To list records whose names start with "al" in the customers table;

 

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SELECT * FROM customers

WHERE AD LIKE 'al%'

To list records whose names end with "al" in the customers table;

 

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SELECT * FROM customers

WHERE AD LIKE '%al'

Let's list the records in the customers table whose name starts with A, the next 2 characters are any letter, and continues with e, and the next letter is unknown. (We will list the ones whose name is Ahmet. :))

 

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SELECT * FROM customers

WHERE ad LIKE 'A _ _ e _'

Let's list the records whose names start with a, b or s.

 

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SELECT * FROM customers

WHERE adLIKE '[abs]%'

Now, let's list the records that do not start with a, b or s.

 

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SELECT * FROM customers

WHERE adLIKE '[!abs]%'

SQL IN USAGE

The IN operator allows you to specify multiple values ​​in the WHERE clause. For example, let's list records whose city is Istanbul and Konya.

 

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SELECT * FROM customers

WHERE city IN ('İstanbul','Konya')

SQL BETWEEN USAGE

The Between operator is used to list records between certain criteria. A number, text or date range can be given. For example, let's list records in the customers table whose points are between 70 and 90.

 

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SELECT * FROM customers

WHERE pointNOT BETWEEN 70 AND 90

To list people whose birth dates are between 01/01/1996 and 01/01/2006;

 

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SELECT * FROM customers

WHERE date of birth BETWEEN '01/01/1996' AND '01/01/2006'

Let's list the records in the customers table whose names are between C and E.

 

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SELECT * FROM customers

WHERE ad  BETWEEN 'C' AND 'E'

SQL ALIASES USAGE

It is used to give a temporary name to the columns in the SQL table.

 

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SELECT ad AS NAME, surname AS SURNAME, date of birth AS [DATE OF BIRTH]

FROM customers

SQL JOIN USAGE

Let's examine the example created using the Orders and Customers tables.

OrderID

CustomerID

OrderDate

10308

2

1996-09-18

10309

37

1996-09-19

10310

77

1996-09-20

 

CustomerID

CustomerName

ContactName

Country

1

Alfreds Futterkiste

Maria Anders

Germany

2

Ana Trujillo Emparedados y helados

Ana Trujillo

Mexico

3

Antonio Moreno Taquería

Antonio Moreno

Mexico

 

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3

4

SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate

FROM Orders

INNER JOIN Customers

ON Orders.CustomerID=Customers.CustomerID;

When we run our query

OrderID

CustomerName

OrderDate

10308

Ana Trujillo Emparedados y helados

9/18/1996

10365

Antonio Moreno Taquería

11/27/1996

10383

Around the Horn

12/16/1996

10355

Around the Horn

11/15/1996

10278

Berglunds snabbköp

8/12/1996

SQL LEFT JOIN USAGE

 

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SELECT Customers.CustomerName, Orders.OrderID

FROM Customers

LEFT JOIN Orders

ON Customers.CustomerID=Orders.CustomerID

ORDER BY Customers.CustomerName

SQL RIGHT JOIN USAGE

 

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SELECT Orders.OrderID, Employees.FirstName

FROM Orders

RIGHT JOIN Employees

ON Orders.EmployeeID=Employees.EmployeeID

ORDER BY Orders.OrderID

SQL SELECT INTO USAGE

The SELECT INTO statement selects data from a table and adds it to a new table. For example, we can create a backup of the customers table named customersbackup.

 

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SELECT *

INTO customersbackup

FROM customers

To add records with only the city "Istanbul";

 

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SELECT *

INTO customersbackup

FROM customers

WHERE city='İstanbul'

SQL CREATE USAGE

To create a new database;

 

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SQL CREATE DATABASE dbname

SQL CREATE TABLE USAGE

It is used to create a new table.

 

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CREATE TABLE customers

(

id int,

ad varchar(255),

surname varchar(255),

address varchar(255),

city varchar(255)

);

 SQL AVG  USAGE

The AVG() function returns the average value of a numeric column. For example, let's find the point average in the customers table.

 

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SELECT AVG(point) FROM customers

In the query below, the name and surname data of the records whose points are above the point average in the customers table are listed.

 

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SELECT ad, surname FROM customers

WHERE point&gt;(SELECT AVG(point) FROM customers);

SQL COUNT USAGE

The COUNT() function returns the number of rows that match the specified criteria. For example, let's find the total number of records in the customers table.

 

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SELECT COUNT(*) FROM customers;

Now let's find out how many different cities there are in the customers table.

 

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SELECT COUNT(DISTINCT city) FROM customers;

Now let's find the number of Customers born in February.

 

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SELECT COUNT (*) FROM customers  WHERE MONTH(date of birth)=2

The following SQL Statement finds the number of orders for "CustomerID" = 7 from the "Orders" table.

 

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SELECT COUNT(CustomerID) AS OrdersFromCustomerID7 FROM Orders

WHERE CustomerID=7

SQL ROUND USAGE

Used to round a decimal number.

 

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SELECT productname, ROUND(price,0) AS RoundedPrice

FROM products

SQL LEN() USAGE

The LEN() function returns the length of a value in a text field. For example, let's print the surname lengths next to the name field in the customers table.

 

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SELECT name,LEN(surname) as surnamelength

FROM customers;

SQL NOW() USAGE

The NOW function returns the system date and time. For example, the following SQL statement will select the product name and price for today from the "Products" table.

 

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SELECT ProductName, Price, Now() AS PerDate

FROM Products;

SQL MAX USAGE

The MAX() function returns the maximum value of the selected column. For example, let's display the highest point in the customers table.

 

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Select MAX(point) AS TheHighestPoint FROM customers

Now let's list the customers with the highest points by name and surname.

 

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SELECT name,surname,point

FROM customers

WHERE point =(SELECT MAX(point)

FROM customers)

SQL MIN USAGE

The MIN() function returns the minimum value of the selected column. Let's display the minimum point in the students table.

 

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Select MIN(point) AS TheLowestPoint FROM students

Now let's list the students with the lowest scores with their first and last names.

 

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SELECT name,surname,point

FROM students

WHERE point =(SELECT MAX(point)

FROM students)

Full Join Usage

In FULL (OUTER) JOIN usage, if we consider the tables as two sets, it returns all the data of the left side table and the right side table as a result.

As a result of this Join, the matching data is shown in the same row, and the unmatched data is returned as empty or "null".

Sample Query;
* You can run this query in the SQL editor and try the result.

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DECLARE @Productler TABLE (Id INT,Product NVARCHAR(50),TurId INT)

DECLARE @Types TABLE (Id INT,Tur NVARCHAR(50))

  
 

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INSERT INTO @Productler(Id,Product,TurId)

VALUES

(1,'Bread',1),

(2,'Bagel',1),

(3,'Gofret',2)

 

  

 

  

 

  

 

  

 

  

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INSERT INTO @Types(Id,Tur)

VALUES

(1,'Bakery Products'),

(2,'Confectionery'),

(3, 'Drink')

 

  

 

  

 

  

 

  

 

  

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SELECT u.Id,u.Product.t.Tur from @Productler u

FULL JOIN @Types t on u.TurId = t.Id

 

  

 

  
         

 

As we see in the example, Beverage, which is a type that is not in the Products table, is also among our results and since there is no product to match, the Product Id and Name are empty.

Group By ve Having Usage

Group by performs grouping according to the desired column or columns in the selected data set.

 Sample Query;
* You can run this query in the SQL editor and try the result.

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DECLARE @Products TABLE (Id INT,Product NVARCHAR(50),TurId INT)

DECLARE @Types TABLE (Id INT,Tur NVARCHAR(50))

 
 

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INSERT INTO @Products(Id,Product,TurId)

VALUES

(1,'Bread',1),

(2,'Bagel',1),

(3, 'Wafer',2),

(4, 'Pogaca',1),

(5, 'Cracker',2),

(6, 'Iced Tea',3),

(2,'Savory Bun',1)

 

  

 

  

 

  

 

  

 

  

 

  

 

  

 

  

 

  

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INSERT INTO @Types(Id,Tur)

VALUES

(1, 'Bakery Products'),

(2, 'Confectionery'),

(3, 'Drink')

 

  

 

  

 

  

 

  

 

  

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SELECT t.Tur,COUNT(u.Id) as 'Piece' FROM @Products u

LEFT JOIN @Types t on u.TurId = t.Id
Group by t.Tur -- We grouped by type

-- HAVING COUNT(u.Id) > 2

Order by 'Piece' desc

 

  

 

  

 

  

 

  

 

Having command is used after Group by command for filtering according to your request. If you open having line which is closed in the sample code above, you can see that categories with product count more than 2 are filtered. 

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