如:
SELECT A.*, B.LOW_LEVEL
FROM
{ oj "DB"."dbo"."A" A INNER JOIN "DB"."dbo"."B" B ON
A."ITEM_NO" = B."ITEM_NO"}
虽然说,去掉{ OJ ... },效果一样
但MS为什么弄出个"{ OJ ... }"来,而且帮助文档上没有任何说明?
虽然有点钻牛角尖,但我想弄清楚!
请给出相关说明,谢谢
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是OUTER JOIN的意思:
ODBC supports the SQL-92 left, right, and full outer join syntax. The escape sequence for outer joins is
{oj outer-join}
where outer-join is
table-reference {LEFT ¦ RIGHT ¦ FULL} OUTER JOIN
{table-reference ¦ outer-join} ON search-condition
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问题是楼主用的是inner join,结果也是inner join的。
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我也找到了，leimin(黄山光明顶) 正确！
Outer Joins
ODBC supports the SQL92 left, right, and full outer join syntax. The escape sequence for outer joins is:
{oj outer-join}
where outer-join is:
table-reference {LEFT ¦ RIGHT ¦ FULL} OUTER JOIN
{table-reference ¦ outer-join} ON search-condition
table-reference specifies a table name, and search-condition specifies the join condition between the table-references.
An outer join request must appear after the FROM keyword and before the WHERE clause (if one exists). For complete syntax information, see “Outer Join Escape Sequence” in Appendix C, “SQL Grammar.”
For example, the following SQL statements create the same result set that lists all customers and shows which has open orders. The first statement uses the escape-sequence syntax. The second statement uses the native syntax for Oracle and is not interoperable.
SELECT Customers.CustID, Customers.Name, Orders.OrderID, Orders.Status
FROM {oj Customers LEFT OUTER JOIN Orders ON Customers.CustID=Orders.CustID}
WHERE Orders.Status='OPEN'
SELECT Customers.CustID, Customers.Name, Orders.OrderID, Orders.Status
FROM Customers, Orders
WHERE (Orders.Status='OPEN') AND (Customers.CustID= Orders.CustID(+))
To determine the types of outer joins that a data source and driver support, an application calls SQLGetInfo with the SQL_OJ_CAPABILITIES flag. The types of outer joins that might be supported are left, right, full, or nested outer joins; outer joins in which the column names in the ON clause do not have the same order as their respective table names in the OUTER JOIN clause; inner joins in conjunction with outer joins; and outer joins using any ODBC comparison operator. If the SQL_OJ_CAPABILITIES information type returns 0, no outer join clause is supported.