R生成mysql select语句

Question

我需要生成复杂的select语句，每次运行脚本时都会根据输入文件进行更改。

我有一个名单列表作为我的过滤器列表，我有一个select语句，已在另一个线程中向我建议。我不确定如何生成我需要的东西，而不是在谷歌接下来的6个小时拼凑它。

我需要为列表中的每个项目创建一个MAX（CASE ...行）。

list <- df$names

list:
1  square
2  ball
3  dog
4  triangle
5  hamster
6  circle
7  yellow
8  cat

suggested SELECT format:
SELECT 
   data.loc
 , data.type
 , MAX(CASE WHEN data.name = 'cat' THEN 1 ELSE 0 END) AS cat
 , MAX(CASE WHEN data.name = 'hamster' THEN 1 ELSE 0 END) AS hamster
FROM 
 data
GROUP BY 
   data.loc
 , data.type

我相信所需的输出将是：

SELECT 
   data.loc
 , data.type
 , MAX(CASE WHEN data.name = 'square' THEN 1 ELSE 0 END) AS square
 , MAX(CASE WHEN data.name = 'ball' THEN 1 ELSE 0 END) AS ball
, MAX(CASE WHEN data.name = 'dog' THEN 1 ELSE 0 END) AS dog
, MAX(CASE WHEN data.name = 'triangle' THEN 1 ELSE 0 END) AS triangle
, MAX(CASE WHEN data.name = 'hamster' THEN 1 ELSE 0 END) AS hamster
, MAX(CASE WHEN data.name = 'circle' THEN 1 ELSE 0 END) AS circle
, MAX(CASE WHEN data.name = 'yellow' THEN 1 ELSE 0 END) AS yellow
, MAX(CASE WHEN data.name = 'cat' THEN 1 ELSE 0 END) AS cat
FROM 
 data
GROUP BY 
   data.loc
 , data.type

Answer 1

我能想到的最简单的方法是

l <- list("Cat", "dog", "bird")
sqlqry <- "SELECT 
   data.loc
 , data.type"
for (i in 1:length(l)) {
  sqlqry <- paste0(sqlqry, sprintf(", MAX(CASE WHEN data.name = '%s' THEN 1 ELSE 0 END) AS %s",l[i], l[i]))
  print(sqlqry)
}
sqlqry <- paste0(sqlry, "your where clause")