PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

Stored Procedures
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action specified and then continue execution of the procedure. Exit handlers exit from
the nearest begin...end block.
The next part of the declare handler specifies when the handler will be called. In this
case, it will be called when sqlstate ‘02000’ is reached.You may wonder what that
means because it seems very cryptic! This means it will be called when no rows are
found.You process a resultset row by row, and when you run out of rows to process, this
handler will be called.You could also specify FOR NOT FOUND equivalently. Other options
are SQLWARNING and SQLEXCEPTION.
The next thing is a cursor. A cursor is not dissimilar to an array; it retrieves a resultset
for a query (such as returned by mysqli_query()) and allows you to process it a single
line at a time (as you would with, for example, mysqli_fetch_row()). Consider this
cursor:
declare c1 cursor for select orderid, amount from orders;
This cursor is called c1.This is just a definition of what it will hold.The query will not
be executed yet.
The next line
open c1;
actually runs the query.To obtain each row of data, you must run a fetch statement.You
do this in a repeat loop. In this case, the loop looks like this:
repeat
...
until done end repeat;
Note that the condition (until done) is not checked until the end. Stored procedures also
support while loops, of the form
while condition do
...
end while;
There are also loop loops, of the form
loop
...
end loop
These loops have no built-in conditions but can be exited by means of a leave; statement.
Note that there are no for loops.
Continuing with the example, the next line of code fetches a row of data:
fetch c1 into this_id, this_amount;
This line retrieves a row from the cursor query.The two attributes retrieved by the
query are stored in the two specified local variables.