为什么这在Microsoft SQL Server Management Studio中有效，而在R中则无效？

Question

我收到此SQL语句：

use MYDATABASE; 
if object_id('tempdb..#mapDT') is not null drop table #mapDT; 
create table #mapDT (SqlDatatype varchar (64), MyNewDataType varchar(64));
insert into #mapDT SELECT 'varchar','type text' UNION ALL SELECT 'datetime','type datetime'UNION ALL SELECT 'tinyint','int64.Type' UNION ALL SELECT 'int','int64.Type' UNION ALL SELECT 'float','type number';
SELECT COLUMN_NAME, DATA_TYPE, 'MyString1' + COLUMN_NAME + 'MyString2' + m.MyNewDataType + 'MyString3' FROM INFORMATION_SCHEMA.COLUMNS C JOIN #mapDT m on m.SqlDatatype = C.DATA_TYPE WHERE TABLE_NAME = 'MYTABLE';

并且它在MS SSMS下运行良好。结果的相关部分是：

MyString1COLUMN01MyString2type textMyString3
MyString1COLUMN02MyString2type datetimeMyString3
MyString1COLUMN03MyString2type textMyString3
MyString1COLUMN04MyString2type textMyString3
MyString1COLUMN05MyString2int64.TypeMyString3
MyString1COLUMN06MyString2type datetimeMyString3
MyString1COLUMN07MyString2type datetimeMyString3
    ...     ...    ...

当我在R下运行它时，我必须忽略use MYDATABASE;，并确保已连接到正确的数据库，这是正确的。但是SQL语句是有问题的。输出：

> library(odbc)
> conn <- dbConnect(odbc(), Driver = "SQL Server", Server = "MYSERVER\\MYINSTANCE", Database = "MYDATABASE", Trusted_Connection = "True")
> dbGetQuery(conn, "
+                   if object_id('tempdb..#mapDT') is not null drop table #mapDT; create table #mapDT (SqlDatatype varchar (64), MyNewDataType varchar(64));
+                   insert into #mapDT SELECT 'varchar', 'type text' UNION ALL SELECT 'datetime', 'type datetime' UNION ALL SELECT 'tinyint', 'int64.Type' UNION ALL SELECT 'int', 'int64.Type' UNION ALL SELECT 'float', 'type number';
+                   SELECT COLUMN_NAME, DATA_TYPE, 'MyString1' + COLUMN_NAME + 'MyString2' + m.MyNewDataType + '},' FROM INFORMATION_SCHEMA.COLUMNS C JOIN #mapDT m on m.SqlDatatype = C.DATA_TYPE WHERE TABLE_NAME = 'MYTABLE';
+                  ")

是data frame with 0 columns and 0 rows。

是否使用“时间表”（即#mapDT）导致数据帧为空？如果是这样，有没有办法让R和/或Python理解/使用它们？

Answer 1

正如Gord Thompson所知道的，代码应包含SET NOCOUNT ON;。因此，

> library(odbc)
> conn <- dbConnect(odbc(), Driver = "SQL Server", Server = "MYSERVER\\MYINSTANCE", Database = "MYDATABASE", Trusted_Connection = "True")
> dbGetQuery(conn, "
+                   if object_id('tempdb..#mapDT') is not null drop table #mapDT; create table #mapDT (SqlDatatype varchar (64), MyNewDataType varchar(64));
+                   insert into #mapDT SELECT 'varchar', 'type text' UNION ALL SELECT 'datetime', 'type datetime' UNION ALL SELECT 'tinyint', 'int64.Type' UNION ALL SELECT 'int', 'int64.Type' UNION ALL SELECT 'float', 'type number';
+                   SELECT COLUMN_NAME, DATA_TYPE, 'MyString1' + COLUMN_NAME + 'MyString2' + m.MyNewDataType + '},' FROM INFORMATION_SCHEMA.COLUMNS C JOIN #mapDT m on m.SqlDatatype = C.DATA_TYPE WHERE TABLE_NAME = 'MYTABLE';
+                  ")

并且在我的情况下，不需要行号，所以我也使用了formals(print.data.frame)$row.names <- FALSE：

> library(odbc)
> conn <- dbConnect(odbc(), Driver = "SQL Server", Server = "MYSERVER\\MYINSTANCE", Database = "MYDATABASE", Trusted_Connection = "True")
> formals(print.data.frame)$row.names <- FALSE
> dbGetQuery(conn, "
+                   if object_id('tempdb..#mapDT') is not null drop table #mapDT; create table #mapDT (SqlDatatype varchar (64), MyNewDataType varchar(64));
+                   insert into #mapDT SELECT 'varchar', 'type text' UNION ALL SELECT 'datetime', 'type datetime' UNION ALL SELECT 'tinyint', 'int64.Type' UNION ALL SELECT 'int', 'int64.Type' UNION ALL SELECT 'float', 'type number';
+                   SELECT COLUMN_NAME, DATA_TYPE, 'MyString1' + COLUMN_NAME + 'MyString2' + m.MyNewDataType + '},' FROM INFORMATION_SCHEMA.COLUMNS C JOIN #mapDT m on m.SqlDatatype = C.DATA_TYPE WHERE TABLE_NAME = 'MYTABLE';
+                  ")
> formals(print.data.frame)$row.names <- TRUE