You can use CHARINDEX to find a specific character or pattern within a column.CHARINDEX...
You can use CHARINDEX to find a specific character or pattern within a column.CHARINDEX...
Return a list of unique countries using DISTINCT. Give the results an alias of unique_c...
preparation: use library() to load the package and use str() to explore the structure o...
How to use filer: must use %>% how to use arrange: Combine filter with arrange: we shou...
Have another look at some useful math functions that R features: abs()[http://www.rdocu...
As for package:how to load package ( we must know the difference between load and insta...
To consult the documentation on the sample()[http://www.rdocumentation.org/packages/bas...
Write a for loop that iterates over all the elements of linkedin and prints out every e...
用subset()從dataframe里面選中符合條件的數(shù)據(jù)subset(my_df, subset = some_condition) 排序:order 直接用order...
這章主要是多表連接的練習(xí),主要涉及到JOIN的用法:SELECT * FROM game JOIN goal ON (id=matchid)表結(jié)構(gòu)如下 The FROM cl...
這個(gè)板塊練習(xí)比較少,主要是GROUP BY和 HAVING 的用法。表結(jié)構(gòu)如下: For each continent show the continent and numb...
這個(gè)版塊的練習(xí)主要是SELECT的一些查詢表結(jié)構(gòu)如下: Show the winners with first name John 注意這里的like,用來查找“John”,...
【Select within Select】部分題目及解析 表結(jié)構(gòu)如下: #List the name and continent of countries in the c...