Is this possible and how would one go about it if it is? Info on the topic is a bit sparse given a Google & Stack search, lots on batch inserts, but nothing solid on batch updates.
Yes it is possible if you insert the correct SQL to do it, but your question is a bit vague.
Rather than trying to update multiple records in a query though, why don't you use a transaction queue instead? Pass your queries in as an array to this function. (requires you have setup an FMDatabase dbQueue of course)
-(BOOL) executeQueryArray:(NSMutableArray*)queryArray {
__block BOOL noErrors = YES;
[self.dbQueue inTransaction:^(FMDatabase *db, BOOL *rollback) {
db.logsErrors = YES;
for (NSString* query in queryArray) {
if (![db executeUpdate:query]) noErrors = NO;
}
*rollback = !noErrors;
}];
return noErrors;
}