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Important SQL Queries

Important SQL Queries with Examples

Learning SQL from time to time is important for depth SQL knowledge. Here we are going to discuss the commonly utilized SQL queries and important ones. When you review this list of SQL queries, you can easily find them mainly for beginners.

 

Acquiring data from particular columns -

 

This query is going to display every detail present from the table bird. If you wish to retrieve the data from particular columns list them after SELECT. Here we are acquiring the information from id and name columns.

 

SELECT id, name

FROM bird;

 

Filtering of data using conditions joined by AND operator –

 

If you desire the data utilizing more than one condition then you can utilize AND operator. In the below example, we are looking for the records having a value of 2 or more in the column age and parrot in the column name. 

 

SELECT id, name, age

FROM bird

Where age>=2 AND name= ‘parrot’;

 

Utilizing DISTINCT to retrieve non repeated records –
 

You can put DISTINCT after the SELECT for retrieving only each kind of record. In the below example, suppose we wish to retrieve records from columns name and color. If the value from these specific columns is similar in more than one record. The query also can be able to return only one of these records. 

 

SELECT DISTINCT name, color

FROM country;

 

Sorting of data according to one column –

 

For sorting data according to one column put the column name after ORDER BY. The default sorting method is done in alphabetic order. But you can also display rows in the order of descending by adding DESC after the column name. In the below example, we are going to sort the data in columns id and name according to the column name.

 

SELECT id, name

FROM bird

ORDER BY name;

 

Looking for values that match a certain pattern –

 

You can use LIKE for searching the values which match a particular pattern. In the below example, we are going to retrieve records from columns id and name which store a strong comprising of a character f in the column name.

 

SELECT id, name

FROM bird

WHERE name LIKE %f%;

 

Utilizing mathematical operators –

 

You can also write queries that perform mathematical calculations using mathematical operators such as + or -. In the below example let's calculate the discounted price.

 

SELECT price – discount

FROM product;

 

Finding the intersection of sets and data –
 

The element INTERSECT returns the intersection of sets and data. Let's see an example.

 

SELECT first-name FROM employee

INTERSECT

SELECT first-name FROM customer;

 

To count the number of rows in a table –

 

You can use COUNT for counting the number of rows present in a table. 

 

SELECT COUNT (id)

FROM product;

 

In the above example, it returns the number of values starting from the column id and which is stored in the table product.

 

Calculation of sum of values in a column –

 

The SUM calculates the sum of values present in a column. Here it returns the values of all the items. 

 

SELECT SUM (price)

FROM item;

 

Thus, these are some of the SQL queries which you need to learn to have basic SQL knowledge.

 

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