Update for 28-02-22 16:30

tech/sql.wiki

@@ -3,6 +3,39 @@
 Stuctered Query Language is a language that describes a method of fetching and
 describing the relationship between different types of data
 
+== Filtering data ==
+
+To filter data we by some specifiers we use the `WHERE` clause. The where
+clause can filter based on the default comparison operators. It can also do
+string comparisons.
+
+This system also works with dates, where all dates are in format `YYYY-MM-DD`.
+
+=== IN ===
+
+To see if an attribute is in a set we can use the `IN` keyword in conjunction
+with a `WHERE` statement. For example,
+`SELECT * FROM holidays WHERE Country IN ('spain', 'portugaul', 'USA');`
+
+=== NOT ===
+
+The `NOT` keyword can be placed before a conditional to specify that we want
+everything that does NOT mean that condition.
+
+=== LIKE ===
+
+`LIKE` lets us filter on patterns. We can use the character `%` to specify a
+wildcard, for any number of characters. We can use the character `_` to give an
+exact number of wildcard characters we are looking for. For example,
+
+`SELECT * FROM Bands WHERE BandName LIKE '%light%';`
+
+will return all bands with the string 'light' in their name.
+
+=== DISTINCT ===
+
+`DISTINCT` filters results by only returning unique values in a column
+
 == Views ==
 
 A view can be created with the following command
@@ -26,6 +59,9 @@ WHERE Price > (SELECT AVG(Price) FROM Products)
 SELECT * FROM [Prodcuts above average price]
   }}}
 
+Views *can* be inserted into, you simply must specify the columns being
+inserted into.
+
 == Acess control commands ==
 
 Two commands for managing access rights