Inserting normal drop down list in Google sheet may be an easy job for you, but, sometimes, you may need to insert a dependent drop down list which means the second drop down list depending on the choice of the first drop down list. How could you deal with this task in Google sheet?
Create a dependent drop down list in Google sheet
The following steps may help you to insert a dependent drop down list, please do as this:
1. First, you should insert the basic drop down list, please select a cell where you want to put the first drop down list, and then click Data > Data validation, see screenshot:
2. In the popped out Data validation dialog box, select List from a range from the drop down list beside the Criteria section, and then click 
button to select the cell values which you want to create the first drop down list based on, see screenshot:
3. Then click Save button, the first drop down list has been created. Choose one item from the created drop down list, and then enter this formula: =arrayformula(if(F1=A1,A2:A7,if(F1=B1,B2:B6,if(F1=C1,C2:C7,"")))) into a blank cell which adjacent the data columns, then press Enter key, all the matching values based on the first drop down list item have been displayed at once, see screenshot:
Note: In the above formula: F1 is the first drop down list cell, A1, B1 and C1 are the items of the first drop down list, A2:A7, B2:B6 and C2:C7 are the cell values which the second drop down list based on. You can change them to your own.
4. And then you can create the second dependent drop down list, click a cell where you want to put the second drop down list, and then click Data > Data validation to go to the Data validation dialog box, choose List from a range from the drop down beside the Criteria section, and go on clicking the button to select the formula cells which are the matching results of the first drop down item, see screenshot:
5. At last, click Save button, and the second dependent drop down list has been created successfully as the following screenshot shown:
