Inner: inner部分对于其子叶来说是parent,所以用 IN 来选出inner node; Leaf:leaf部分不是parent,所以不会出现在parent中,可以用 NOT IN 来选出leaf node。 --- Method 1 ---SELECTCASEWHENpISNULLTHENCONCAT(n,' Root')WHENnNOTIN(SELECTpFROMBSTWHEREpISNOTNULL)THENCONCAT(n,' Leaf')ELSECONCAT(n,'...
前段时间准备找工作,把hackrank上的SQL相关题目都做了一遍,五十多道,基本上涵盖了SQL transaction的所有知识点了,找工作前准备SQL相关的话,可以看看。 题目在 hackerrank.com/domains/ 1 Revising the Select Query I Query all columns for all American cities in CITY with populations larger than 100000. The ...
Solve the problems of the Hacker Rank website on SQL, in order according to what was arranged on the site with the title of the problem. With pictures of tables. https://www.hackerrank.com/ - AhmedKhaled146/Learn-SQL-with-HackerRank
-- multiple distinct counts in one query tend to be slow SELECT count(distinct a), count(distinct b), count(distinct c) FROM table_abc; 对于这类查询,worker 上产生的 select distinct 语句本质上会产生要传输到 coordinator 的行的 cross-product(叉积)。 为了提高性能,您可以选择进行近似计数。请...
RANK DENSE_RANK LAG LEAD CUME_DIST PERCENT_RANK NTILE If you're looking to enhance your Spark SQL knowledge and use cases, these functions will come in handy for various types of data analysis. Let's start with a quick introduction to each of these functions. ...
# 确保fake_key不存在 redis> EXISTS fake_key (integer) 0 # 以fake_key作BY参数,不排序,只GET name 和 GET password redis> SORT user_id BY fake_key GET # GET user_name_* GET user_password_* 1) "222" # id 2) "hacker" # user_name 3) "hey,im in" # password 4) "59230" 5) ...
Explore SQL vs. T-SQL differences, their unique features, and use cases in database management, development, and advanced SQL Server operations.
但是为什么使用子查询也不提供重复的值呢?考虑产生相同结果的result语句如下 select ID, Name, Description where ID IN on tblProducts.I 浏览1提问于2018-12-22得票数 1 3回答 为什么这两个SQL查询不做同样的事情呢? 、、以下是来自本页的Hacker Rank SQL...
XKCD's author Randall Munroe is a smart cookie. If this comic were being written today, the hacker mom character probably would have said this instead: Input Should Still BeValidated Validation is not the same thing as sanitation. Prepared statements can prevent SQL Injection, but they cannot...
As a rank-and-file developer, though, who’s worked with both Web SQL and IndexedDB, I can’t shake the feeling that the W3C made the wrong choice here. Let’s remember what Web SQL actually gave us: SQLite in the browser. Seriously, right down to thesqlite_mastertable,ftsindexes for...