A database is a part of knowledge base. for me, knowledge is an composition of two parts : schema ( ontology ) + instance (individuals).  if your database has schema, the answer is yes.

I agree with Samir.. But KB has evolved..a 30 years ago KB is not what we define as a KB today

Then, Knowledge base , KB was  a DB+IE ( IE is inference engine ), IE convert  the  Data in to useful Knowledge..

Data models what we had 30 years ago, stored data as  "flat data", using hierarchical or Relational. They created Structured data..But most of the data we store today are Semi or unstructured data ( Facebook) , and hence data models that can manipulate unstructured data are necessary..

Data base is the basic requirement for knowledge base, almost in all fields of research, specialy like field of agricalter, weather, climate change, sesmic study to know sunami and volcanic eruptions and many more. For development of imparical formulas, models development, plotting graph to reach, to some conclusion data base is the only base of prime importance.

I agree with all the previous comments. You can also take a look at a very nice presentation on Slideshare (see attached link).

http://www.slideshare.net/mcjenkins/knwoedgebase-vs-database

Texts can be somehow prepared by the readers and users to ease the semantic search: here is how it is done in the Lexicon of Arguments:

Problem/definition/concept – solution/proposal – counter argument – scientific camp/ism

500 characters max. No answer without indication of the source is accepted. An example

Field: ecology/climate change

Solution/proposal/author1: painting n% of the roofs white will reduce global warming by m%.

Scientific camp: climate model A

Non-mentioned concepts: geographical latitude, higher atmospheric layers

Source/page: URL/access date

1st Counter argument

Author2Vsauthor1: reflected sunlight from additional n% white roofs destroys ozone in the higher atmospheric layers by k%

Scientific camp: climate model B

Non-mentioned concepts: geographical latitude

Source/page: URL/access date

2nd Counter argument

Author3Vsauthor2/author3Vsauthor1: houses with white roofs in higher latitudes cool down in winter and need more heating. N% white roofs in latitude k -> M% more carbon dioxide.

Scientific camp: climate model C

Non-mentioned concepts: higher atmospheric layers

Source/page: URL/access date

Then you can search: “What are the drawbacks of climate model A?” – “White roofs, climate change, counter arguments” – “Vs authorX” etc.

Non-mentioned concepts: why are they important? Because of the semantic search (Semantic Web). You might not find crucial information because an author did not mention an important counter position.

So the users have to cooperate by using the format. Anyway the Lexicon of Arguments provides simple automatic forms. Mendeley, zotero, Citavi, EndNote are easily imported/exported.

Here is an example from the Lexicon for “VsChomsky”:

http://philosophy-science-humanities-controversies.com/search.php?suche3=VsChomsky