It is not likely that you will find all the articles you want in one database. For most research, it will be necessary to look in two or three databases to be sure you have found the appropriate materials.
Each database has its own search terms so it may be necessary to use different words to search for the same idea each time you start researching in a new database.
Example: U.S. Civil War or War of the Rebellion
Language changes over time and it might be helpful to use synonyms when searching a large period of time.
Example: Consumption and Tuberculosis are the same illness, but different
different words were used to refer to it in different centuries