mysql - 在 R 中运行 MySQL 查询，其中要搜索的值在 DF 中

Question

我有一个包含多个列的 DF，但有一列是某些预处理阶段的结果，该列包含我需要使用 MySQL 查询进行搜索的值。

如何让查询直接读取包含此信息的列或另一个 DF，而不是手动添加它们？

DF 示例:

id
3061945
7392492
7491277
7855936
8125589
7060737
5614627
7597607

查询:

select c.Id as sfdcContactID,
    c.FirstName, 
    c.ID__c as uid 
from Contact as c 
where c.ID__c in ('values to be looked based on the DF’); 

Answer 1

由于数据帧中可能有数千甚至数百万个值，请考虑将数据帧导出到 MySQL 临时表，然后将其加入您的查询中。以下是使用数据库 API 或命令行最终创建查询结果数据框的几种方法。

RODBC

# REPLACES TEMP WITH EVERY CALL
sqlSave(conn, "temptablename", df, append = FALSE)   

# RUNS QUERY AND IMPORTS RESULTS INTO DATAFRAME
newdf <- sqlQuery(conn, paste0("SELECT c.Id as sfdcContactID, c.FirstName, c.ID__c as uid",
                               " FROM Contact c",
                               " INNER JOIN temptablename t ON c.ID__c = t.id"))

RMySQL

# REPLACES TEMP WITH EVERY CALL
dbWriteTable(conn, "temptablename", df, overwrite = TRUE)

# RUNS QUERY AND IMPORTS RESULTS INTO DATAFRAME
newdf <- dbGetQuery(conn, paste0("SELECT c.Id as sfdcContactID, c.FirstName, c.ID__c as uid",
                                 " FROM Contact c",
                                 " INNER JOIN temptablename t ON c.ID__c = t.id"))

命令行

R - CSV 导出

write.csv("path/to/file.csv", df)

SQL (另存为 .sql 文件)

# IMPORT CSV FILE TO TABLE
LOAD DATA LOCAL INFILE '/path/to/file.csv'
INTO TABLE temptablename
FIELDS TERMINATED BY
ENCLOSED BY '"'
LINES TERMINATED BY '\r\n';

# EXPORT QUERY TO CSV FILE
SELECT c.Id as sfdcContactID, c.FirstName, c.ID__c as uid
FROM Contact c
INNER JOIN temptablename t ON c.ID__c = t.id
INTO OUTFILE '/path/to/output.csv' 
FIELDS ENCLOSED BY '"' 
TERMINATED BY ',' 
LINES TERMINATED BY '\r\n';

R - CMD/Shell 调用 mysql 客户端

system("mysql -u username -p password db_name < /path/to/file.sql")

df <- read.csv("/path/to/output.csv")