i want to know a bit more about cursors and the technical way they are realized. my understanding is, that cursors are pointers on a result-set within the ram. the result-set is small (comparing to the table the rows are from) and the sql which perform the result-set is executed only one time (i hope :o) ), right?
So what we have is a small result-set within a location the cpu has the fastest way to grab rows from this result-set.
why should this cursors (used in for loops) not be more efficient than ordinary sql-queries (in for loops)?
ordinary queries grap the rows from the hard-disk, where the cpu needs more time to grap them. and erery time the sql-query is executed the a full table-scan must be performed to find the row.
cursors (used in for loops):
- sql-query to get the result-set is executed one time, to make a result set (in the initialsation-part of procedure)
- one small result-set
- fastest way for a cpu to grap the data, because they are in the ram
ordinary queries (used in for loops):
- executed to get on row per query
- in every execution the whole table has to be scaned to get one row, so there is no result-set to crawl over
- no fast way for the cpu to grap the data, because data is on harddrive
what du you think about what my understanding of cursors is. am i right?
please let me know.