conscious [ˈkɔnʃəs]
a.意识到的，自觉的；神志清醒的；有意的
encyclopedia [enˌsaikləuˈpi:diə]
n.百科全书
aspect [ˈæspekt]
n.方面；朝向，方向;面貌,外观
poor-performing code that is diffi cult to maintain
envision [enˈviʒən]
v.想象；预想
But in this chapter,as mentioned, I’ll deal only with the fundamentals of querying. ThroughoutBut keep in mind that in practice, the actual physical processing of a query might be very different than the logical one.
optimizer
n.优化程序
determine [diˈtə:min]
vt.确定；决定；使下决心 vi.下决心
algorithm [ˋælɡeriðəm]
工作步骤，运算法则，推导：解决某些类型数学问题的机械操作，逐步解决问题的方法，如对诊断的探索
In contrast,
contrast [ˈkɔntrɑ:st]
n.对比；反差 vt.对比 vi.(with)形成对比
aforementioned
adj.上述的(前面提到的)
delve [delv]v.深入探究，钻研
Without further ado, let’s delve into logical query processing phases
clause [klɔ:z]
n.(法律文件等的)条款；从句，分句
In SQL, the fi rst clause that is processed is the FROM clause,while the SELECT clause, which appears fi rst, is processed almost last.
caller [ˈkɔ:lə]
n.呼喊者；访问者
specify [ˈspesifai]
vt.明确说明，具体指定
corresponding [ˌkɔriˈspɔndiŋ]
a.相应的，相当的；符合的，一致的
Each step generates a virtual table that is used as the input to the following step. These virtual tables are not available to the caller (client application or out is returned to the caller. If a certain clause is not specifi ed in aer query). Only the table generated by the fi nal step query, the corresponding step is simply skipped.
sense [sens]
n.感官(觉)；判断力，见识；意思 vt.觉得
populate / ˈpɔpjuleɪt; ˋpɑpjəˏlet/
v [Tn esp passive 尤用於被动语态] (a) live in (an area) and form its population居住於（某地区）（而构成其人口成分）
nitty-gritty/ ˏnɪtɪ ˈgrɪtɪ; ˏnɪtɪˋɡrɪtɪ/
n
the nitty-gritty [sing](infml
口) the basic facts or realities of a matter 基本事实; 实情: Let's get down to (discussing) the nitty-gritty.
咱们着手探讨实际情况吧.
digress [daiˈgres]
vi.离题
The possible values of a predicate (logical expression) in SQL are TRUE, FALSE, and UNKNOWN.
UNKNOWN logical results and NULLs are treated inconsistently in different elements of
the language. For example, all query fi lters (ON, WHERE, and HAVING) treat UNKNOWN
like FALSE. A row for which a fi lter is UNKNOWN is eliminated from the result set. On
the other hand, an UNKNOWN value in a CHECK constraint is actually treated like TRUE.
Suppose you have a CHECK constraint in a table to require that the salary column be
greater than zero. A row entered into the table with a NULL salary is accepted because
(NULL > 0) is UNKNOWN and treated like TRUE in the CHECK constraint.
as if
好像，仿佛
spare [speə]
a.备用的；多余的 vt.抽出(时间) n.备用品
