for循环仅检查向量中的最后一个值以使用R检查SQL Server中的重复项？

Posted 2023-03-22

【中文标题】for循环仅检查向量中的最后一个值以使用R检查SQL Server中的重复项？

【英文标题】：for Loop only check the last value in the vector to check duplicates in SQL Server with R?

【发布时间】：2021-12-30 03:24:43

【问题描述】：

library(odbc)
library(DBI)
library(pool)
myDatabase <- 'MyDB'
myDriver <- 'SQL Server'
myServer <- 'localhost\\SQLEXPRESS'

con <- pool::dbPool(odbc::odbc(), Driver = myDriver,
                    Server = myServer,
                    Database = myDatabase,
                    Trusted_Connection = 'True')

Caddy_id <- c("C1","C2","C3","C4","C5","C6","C7","C8","C9","C10")

for(i in 1:length(Caddy_id))
  
check_duplicate <- dbGetQuery(con,paste0("DECLARE @container AS INT = 0
                                            IF EXISTS(SELECT 1 FROM dbo.P1000_Packing WITH(NOLOCK)
                                              WHERE Caddy_1 = '",Caddy_id[i],"' OR
                                                    Caddy_2 = '",Caddy_id[i],"' OR
                                                    Caddy_3 = '",Caddy_id[i],"' OR
                                                    Caddy_4 = '",Caddy_id[i],"' OR
                                                    Caddy_5 = '",Caddy_id[i],"' OR
                                                    Caddy_6 = '",Caddy_id[i],"' OR
                                                    Caddy_7 = '",Caddy_id[i],"' OR
                                                    Caddy_8 = '",Caddy_id[i],"' OR
                                                    Caddy_9 = '",Caddy_id[i],"' OR
                                                    Caddy_10 = '",Caddy_id[i],"')
                                              BEGIN
                                                   SET @container = 1
                                              END
                                            SELECT @container;"))


check_duplicate

我想用 R 检查 SQL Server 中所有重复值，但只能检查向量 Caddy_id 中的最后一个值。

为什么只有值10返回1，而另外一个值即使存在于sql表中也会返回0？

此表返回 1

.

但是这个表返回 0

如果我改变矢量Caddy_id <- c("C0","C1","C2","C3","C4","C5","C6","C7","C8","C9") 它还返回 1

【问题讨论】：

因为你每次循环都在替换check_duplicate变量的值，所以循环退出时只对应Caddy_id[I]的最后一个值，也就是@987654329 @。一种选择是使用另一个名为（比如）result 的变量，在循环之前将其设置为 0，如果check_duplicate 在循环内为 1，则将其设置为 1。还有其他选项（例如使用 SQL in，或者读取您的表并在 R 中查找向量变量），但这看起来对您的代码的更改最少

【参考方案1】：

目前，您的查询在每次迭代中自行运行，其中 @container 每次都重置为零。因此，只会保留最后一次运行的计数，并且每次都会替换 check_duplicate。

但是，考虑通过为每个球童 ID 构建一个聚合计数向量列表来计算 R 中的重复项。确保还使用参数安全地运行查询，其中一种方法包括 sqlInterpolate。

Caddy_id <- c("C1","C2","C3","C4","C5","C6","C7","C8","C9","C10")

sql = "SELECT COUNT(*) AS [count]
       FROM dbo.P1000_Packing
       WHERE Caddy_1  = ?cad_id OR
             Caddy_2  = ?cad_id OR
             Caddy_3  = ?cad_id OR
             Caddy_4  = ?cad_id OR
             Caddy_5  = ?cad_id OR
             Caddy_6  = ?cad_id OR
             Caddy_7  = ?cad_id OR
             Caddy_8  = ?cad_id OR
             Caddy_9  = ?cad_id OR
             Caddy_10 = ?cad_id"

check_duplicates <- sapply(
    Caddy_id, 
    function(i) 
        qry <- sqlInterpolate(con, sql, ?cad_id = i)
        dbGetQuery(con, qry)$count
    
)

total_duplicates <- sum(check_duplicates, na.rm = TRUE)

---

另一种 SQL 查询：

SELECT COUNT(*) AS [count]
FROM dbo.P1000_Packing
WHERE ?cad_id IN (
     Caddy_1, Caddy_2, Caddy_3, Caddy_4, Caddy_5,
     Caddy_6, Caddy_7, Caddy_8, Caddy_9, Caddy_10
)

【讨论】：

@Taufiq 如果这回答了你的问题，那么请“接受”它。