A short list of SQL commands
So for starters, here are some examples of the SQL language scheme. In these examples, there is one database, called AdventureWorks with two tables of data, Personal-Info, and Department
Use AdventureWorks (name of the database)
Contact ID (category to look for)
Position (category to look for)
FirstName (category to look for)
LastName (category to look for)
From Personal-Info (table name with the relevant data)
When the query is executed the results will show the Contact ID, the position, the First Name, and the Last Name. This is a generic sql statement because it does not filter anything.
Example #2: Here is an example of a filter in action.
From Personal-Info where Position = "Programmer" (The where Position = "Programmer is the filter)
This query will show only the results to only those persons who are programmers. Technicians, for example, would be excluded.
Example #3 (using two tables to get information)
Where Personal-Info.ContactId = Department.ContactID (You are making the connection between the two tables by using the ContactID)
In this example, you are searching two tables to get the required information, which is the ContactID, the Firstname, Lastname, and the DepartmentName. This is a multi-filter technique because it connects the query to two tables to get the required information. You can read more about SQL at An Overview of Structured Query Language.