full table scan
英漢例句
- The predicates in the query in Listing 7 are weakly selective so that a full table scan of the pdbxml table is required.
清單 7 中查詢的謂詞選擇性較弱，因此需要對 pdbxml 表進(jìn)行全表掃描。 - Most often, you want only a small subset of the data in the table, so a full table scan wastes a lot of disk I/O and therefore time.
通常來說，您可能衹希望獲得表中數(shù)據(jù)的一個(gè)子集，因此全表掃描會浪費(fèi)大量的磁磐 I/O，因此也就會浪費(fèi)大量時(shí)間。 - If there is no index on ucname, the DBMS still does a full table scan, but it need not do any further processing on the data to determine whether or not it satisfies the query.
如果沒有爲(wèi) ucname 創(chuàng)建索引，DBMS 仍然執(zhí)行全表掃描，但是不會對數(shù)據(jù)進(jìn)行進(jìn)一步処理來判斷其是否滿足查詢。