相关疑难解决方法(0)

我读了一篇关于JOINS的好文章,"INNER JOIN"和"OUTER JOIN"有什么区别？但我不认为这有助于我的问题.

我想将两个select语句组合成一个select语句AND,使其对任何要查询的数据库都有效.

这就是我所拥有的

SELECT
(SELECT COUNT(*) 
                        FROM dbo.sem_computer, [dbo].[V_SEM_COMPUTER], dbo.IDENTITY_MAP, dbo.SEM_CLIENT,dbo.SEM_AGENT,dbo.PATTERN
                        WHERE [dbo].[V_SEM_COMPUTER].COMPUTER_ID = SEM_COMPUTER.COMPUTER_ID
                        AND dbo.SEM_CLIENT.GROUP_ID = IDENTITY_MAP.ID
                        AND dbo.SEM_CLIENT.COMPUTER_ID = SEM_COMPUTER.COMPUTER_ID
                        AND SEM_COMPUTER.COMPUTER_ID = dbo.SEM_AGENT.COMPUTER_ID
                        AND dbo.PATTERN.PATTERN_IDX = dbo.SEM_AGENT.PATTERN_IDX
                        AND Name like '%Staten Island%'
                        AND dbo.SEM_AGENT.AGENT_VERSION LIKE '11.%'
                        AND dbo.SEM_COMPUTER.OPERATION_SYSTEM LIKE 'Windows%') AS 'Windows-SEP-11',
(SELECT COUNT(*) 
                        FROM dbo.sem_computer, [dbo].[V_SEM_COMPUTER], dbo.IDENTITY_MAP, dbo.SEM_CLIENT,dbo.SEM_AGENT,dbo.PATTERN
                        WHERE [dbo].[V_SEM_COMPUTER].COMPUTER_ID = SEM_COMPUTER.COMPUTER_ID
                        AND dbo.SEM_CLIENT.GROUP_ID = IDENTITY_MAP.ID
                        AND dbo.SEM_CLIENT.COMPUTER_ID = SEM_COMPUTER.COMPUTER_ID
                        AND SEM_COMPUTER.COMPUTER_ID = dbo.SEM_AGENT.COMPUTER_ID
                        AND dbo.PATTERN.PATTERN_IDX = dbo.SEM_AGENT.PATTERN_IDX
                        AND Name like …

我的一位同事的文件夹/目录中有很多sql陈述。该文件夹也由他每天更新。我想sql为期货同事记录这些声明。但是，我正在寻找一种使该过程“自动化”的方法。我想crontab每周使用一次并运行一个R-Markdown文件，该文件会自动更新现有R-Markdown文件。

我的方法如下：

path = "c:/SQL_files/"
out.file<-""
file.names <- dir(path, pattern =".sql") # here I changed `.txt` to `.sql`
for(i in 1:length(file.names)){
file <- read.csv2.sql(file.names[i],header=TRUE, sep=";",    stringsAsFactors=FALSE)
  out.file <- rbind(out.file, file)
}


# That second approach comes very close, but just generates a `.txt` for the first
#`.sql` file in the directory with the error:

   Error in match.names(clabs, names(xi)) : 
   names do not match previous names 

文件在哪里：

 [1] "c:/SQL_files/first.sql"                                            
 [2] "c:/SQL_files/second.sql" …

SELECT *
  FROM notifications
  INNER JOIN COMMENT
    ON COMMENT.id = notifications.source_id
      WHERE idblog IN (SELECT blogs_id
        FROM blogs
        WHERE STATUS = "active")
  INNER JOIN reportmsg
    ON reportmsg.msgid = notifications.source_id
      WHERE uid =: uid
  ORDER BY notificationid DESC
  LIMIT 20;

在这里,我INNER JOIN荷兰国际集团notifications与comment和reportmsg; 然后过滤内容WHERE.

但我的问题是,第一INNER JOIN[即与comment],在加入之前notifications有comment,我想匹配notifications.idblog与blogs.blogs_id 和 SELECT只有那些行,其中blogs.status = "active".

为了更好地理解上面的代码:

这里,INNER JOIN与comment我想SELECT …

我有多个连接,包括mysql中的左连接.有两种方法可以做到这一点.

1. 我可以在每次加入后立即设置"ON"条件:

   select*from A join B ON(A.bid = B.ID)join C ON(B.cid = C.ID)join D ON(c.did = D.ID)

2. 我可以将它们全部放在一个"ON"子句中:

   select*from A join B join C join D ON(A.bid = B.ID AND B.cid = C.ID AND c.did = D.ID)

哪种方式更好？

如果我在查询中需要左连接或右连接,它是否不同？

我访问过许多网站，找到关于哪个更好的答案，即ANSI或非ANSI语法。这两个查询有什么区别？

select a.name,a.empno,b.loc
from tab a, tab b
where a.deptno=b.deptno(+);

和：

select a.name,a.empno,b.loc
from tab a 
left outer join tab b on a.deptno=b.deptno;

在两种情况下结果都是相同的。第二个查询也更长。哪一个更好？

假设是否基于需要连接它们的条件在上面的查询中添加了另一个表Salgrade？..谁能假设一张桌子并给我解释

我有以下问题。我有 2 个表想要加入“TableALong”和“TableBLong”

TableALong

ID, Name, Store,Age
1, John, Walmart, 5
2, Johnny, Walmart, 8
3, Johnny, Target , 10
4, Bill, Shoppers, 2
5, Joe, Target, 3

TableBLong
ID, Name, Store, StoreAddress
1, John, Walmart, 35353 Address
1, John, Walmart, 53544 Address
2, Johnny, Walmart, 35353 Address

在加入之前，我想做一些类似 ALIAS 的事情，我有这样的事情：

SELECT A.ID, A.NAME, A.STORE, A.AGE, B.STOREADDRESS
FROM TableALong as A, TableBLong as B
ON A.NAME = B.NAME and A.STORE = B.STORE

这在oracle中是无效的。让它在 oracle 中运行的正确查询是什么？我认为这是我想要的左连接？（连接后，TableALong 中的每一项都会有多行。）