SQL AND: Operation and examples

Sql AND is an operator used to make a request with certain parameters. The corresponding input is only taken into account if all the conditions indicated are met.

Sql AND : Why use it?

The SQL operator AND is used in the Structured Query Language for filter the results of a clause according to specific criteriathus allowing precise research. Just like the operator SQL or, AND is mainly used in the request WHERE And can be combined with other operators. These two operators are based on Boolean algebra, which operates on « true » or « false » logical values. However, OR tends to expand research results more than and.

Sql AND : syntax and operation

Sql AND is used in a Select request in combination with a condition WHERE. Syntax presents itself as follows:

SELECT colonne1, colonne2, …
FROM nom_de_la_table
WHERE condition1 AND condition2 AND condition3 AND …;

Thanks to the SQL command SELECTyou select all the columns to consider for your request. It is also possible to specify a single column. The FROM clause allows you to locate the corresponding table for your request. With Where, you list the conditions that the entries must fulfill to be displayed. The SQL operator AND Displays a result only if all the conditions are metwhile OR Also posted entries if at least one of the conditions is met.

Sql AND : Example of the operator use

SQL's function and usefulness AND are more easily understandable through an example. Imagine a company with several subsidiaries around the world. In a dedicated table, we record an identifier for each subsidiary, the city, the country and the number of employees. The name of our table is « subsidiaries ».

In the next step, we launch a request and use the operator AND as an exclusion criterion for research. Thus, only the subsidiaries located in France and employing more than 20 people must be displayed. The corresponding declaration then presents itself as follows:

SELECT ID, Ville, Pays, Employés
FROM Filiales
WHERE Pays="France" AND Employés > 20;

The result is as follows:

Using the operator ANDwe excluded the subsidiary with ID 2, because it employs less than 20 people. Subsidiaries 4 and 5 have not been taken into account, because they are not located in France.

Combine operators AND And OR

It is possible to combine SQL AND with the operator OR. To do this, we again use the table above called « subsidiaries ». This time, however, we want to take into account all the subsidiaries which have more than 20 employees and which are in France or Germany. For this, we must use a parenthesis. The corresponding code presents itself as follows:

SELECT ID, Ville, Pays, Employés
FROM Filiales
WHERE (Pays="France" OR Pays="Allemagne") AND Employés > 20;

Here is the result:

Operators similar to SQL AND

In addition to the operator ORthere is another alternative to SQL AND which allows you to search for a set of data according to certain criteria. The operator NOT acts as an exclusion criterion and selects entries that do not meet a certain condition. Thus, for the first example mentioned above, you could use this operator to display, among other things, all the subsidiaries that are not in France.