The database is complete. If you cannot find the place you are looking for, please see the following questions.
As Newfoundland did not become a province of Canada until 1949, it was not included in the Canadian census for this time period.
These place names appear in the database with the abbreviations St or Ste and a hyphen, for example, St-Vincent, St-Stephen, Ste-Anne-de-Sorel, etc. The exception is the County and City of Saint John, New Brunswick, which is always spelled in full.
If the place you are researching does not appear in the database, it is usually because it was a smaller town or village, which were not enumerated separately. Those places were enumerated within the surrounding area, depending on how the province was divided at the time. In Ontario, the sub-districts usually correspond with townships; in New Brunswick, with parishes; in Manitoba, with rural municipalities; in Quebec, with townships and parishes; in Prince Edward Island, with Lots. There was no standardized system for the division of Nova Scotia and the districts west of Manitoba.
Examples: The village of Bell's Corners in Carleton County, Ontario, was enumerated within Nepean Township. The village of Petit Rocher in Gloucester County, New Brunswick, was enumerated within Beresford Parish.
It is also possible that your town, city or village did not exist in the period of interest to you, it had a different name at that time or it was in an isolated region that was not enumerated.
The following sources can assist you in identifying a relevant province and district/county, and sometimes also the sub-district:
Prior to the first Dominion Census in 1871, census enumerations were conducted in different areas in various years. Many of those early records have not survived, including portions of the 1851 returns. As provinces joined Confederation, they were included in subsequent federal census returns, for example Prince Edward Island in 1881.