What is a Switch Statement in computer language?

About

A switch is a multi-way conditional branch that permits to control the flow

Syntax

There is basically two syntax:

the value_switch where the possibilities are scalar values
the expression_switch where the possibilities are expressions

In some language such as SQL, the case word is used in place of switch

Value Switch

Php:

switch ($i) {
    case 0:
        echo "i equals 0";
        break;
    case 1:
        echo "i equals 1";
        break;
    default:
       echo "i is not equal to 0 or 1";
}

Sql

CASE  Promotions."Promo Subcategory"
WHEN  'TV commercial'          then 'Commercial'
WHEN  'TV program sponsorship' then 'Sponsor'
ELSE  'Default'
END

Expression Switch

Php:

switch (true) {
    case $start - $offset === 1:
        print "A";
        break;
    case $start - $offset === 2:
        print "B";
        break;
}

Sql:

CASE WHEN "Sales Facts"."Amount Sold" > 600000  THEN 'Big'
     WHEN "Sales Facts"."Amount Sold" > 300000  THEN 'Middle'
     ELSE 'Small' END

Fall through behavior

The switch statement has fall through behavior therefore the break is important.

If you omit the break from a case, and that case matches or runs, execution will continue to the next case.

Without break

color = "green"
switch (color) { 
    case "blue": 
         console.log("blue");
    case "green": 
          console.log("green");
    case "red": 
    case "orange":
         console.log("red or orange");
    default:
         console.log("default");
}

Result: You will see all console output from the green case

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With ''break'

color = "green"
switch (color) { 
    case "blue": 
         console.log("blue");
         break;
    case "green": 
          console.log("green");
          break;
    case "red": 
    case "orange": 
          console.log("red or orange");
          break;
    default:
         console.log("default");
}

Result: you will see only one output

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