【SQL进阶教程】让SQL飞起来
不管是减少排序还是使用索引，抑或是避免中间表的使用，都是为了减少对硬盘的访问。
使用高效的查询在SQL中，很多时候不同代码能够得出相同结果。从理论上来说，得到相同结果的不同代码应该有相同的性能，但遗憾的是，查询优化器生成的执行计划很大程度上要受到代码外部结构的影响。
参数是子查询时，使用EXISTS
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【SQL进阶教程】HAVING子句又回来了
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整理一下在调查集合性质时经常用到的条件。这些条件可以在HAVING子句中使用，也可以通过SELECT子句在CASE表达式里使用。
各队，全体点名需要做的是查出现在可以出勤的队伍。可以出勤即队伍里所有队员都处于“待命”状态。使用的是下面这张表。
1234567-- 谓词SELECT team_id
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[LintCode] Problem 617 - Maximum Average Subarray II
Given an array with positive and negative numbers, find the maximum average subarray which length should be greater or equal to given length k.
NoteIt
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[LeetCode] Problem 643 - Maximum Average Subarray I
Given an array consisting of n integers, find the contiguous subarray of given length k that has the maximum average value. And you need to output the
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[LeetCode] Problem 522 - Longest Uncommon Subsequence II
Given a list of strings, you need to find the longest uncommon subsequence among them. The longest uncommon subsequence is defined as the longest subs
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[LeetCode] Problem 521 - Longest Uncommon Subsequence I
Given a group of two strings, you need to find the longest uncommon subsequence of this group of two strings. The longest uncommon subsequence is defi
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The English We Speak 3
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In black and whiteit’s official - it’s been printed or written down - so there is no dispute!
ExamplesI have it here in black and white - I’ve got the
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【SQL进阶教程】用SQL处理数列
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生成连续编号思考一下如何使用SQL生成连续编号。例如生成0～99这100个连续编号。首先生成一张存储了各个数位上数字的表“数字表”。
这样，就可以通过对两个Digits集合求笛卡尔积而得出0～99的数字。
1234SELECT D1.digit + (D2.digit * 10) AS seqFR
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【SQL进阶教程】EXISTS谓词的用法
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谓词是一种特殊的函数，返回值是真值。谓词逻辑提供谓词是为了判断命题的真假。参数是行数据的集合。在EXISTS的子查询里，SELECT子句的列表可以有下面这三种写法。
通配符：SELECT *
常量：SELECT ‘这里的内容任意’
列名：SELECT col
在SQL中，为了表达全称量化，需要将
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[LeetCode] Problem 520 - Detect Capital
Given a word, you need to judge whether the usage of capitals in it is right or not.
We define the usage of capitals in a word to be right when one of
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