collections - push_back() and push_front() in Java -
क्या जावा में कोई संग्रह वर्ग है, जो push_back () और push_front ) तरीकों?
वर्ग ने पहले / अंतिम जोड़ दिया है), getFirst / last () और निकालेंप्रथम / अंतिम ()।
oracle - The fastest way to check if some records in a database table? -
I have a big table to work with. I have to see that there are some records whose parent_id is equal to my passing value. Currently I do this by implementing "my_table using select count (*) where parent_id =: id"; If the result> 0, it means that they exist. Because this is a very large table, and I do not care what the actual number of records present, I just want to know if it exists, so I think count (*) Bit is disabled. How do I apply this requirement most quickly? I'm using Oracle 10. # Tips for Hibernation & amp; Tricks It suggests writing in such a way: Integer number = (integer) session .createQuery ("Select Count (*) to ...."). UniqueResult (); I do not know what is the magic of the unique rule? Why does it fast? To compare, select "1 from mytable where parent_id = passId and rowrum", which is more efficient? If you are not interested in the number of records, then there is an EXISTS query one: Select 'y'
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