adding lec10 for db

cst363/lec/lec10.md

@@ -0,0 +1,43 @@
+# lec10
+
+This lecture has a corresponding lab excercise who's instructions can be found in `triggers-lab.pdf`.
+
+## What is a trigger
+
+Something that executes when _some operation_ is performed
+
+## Structure 
+
+```
+create trigger NAME before some_operation
+when(condition)
+begin
+	do_something
+end;
+```
+
+To explain: First we `create trigger` followed by some trigger name.
+Then we have to denote that this trigger should fire whenever some operation happens.
+This trigger then executes everything in the `begin...end;` section _before_ the new operation happens.
+
+> `after`
+
+Likewise if we want to fire a trigger _after_ some operation we ccan just replace the before keyword with `after`.
+
+> `new.adsf`
+
+Refers to _new_ value being added to a table.
+
+> `old.adsf` 
+
+Refers to _old_ vvalue being changed in a table.
+
+	
+## Trigger Metadata
+
+If you want to look at what triggers exist you can query the `sql_master` table.
+
+```
+select * from sql_master where name='trigger';
+```
+