OleDb SQL 查询中的两个内部联接

问题描述

我正在尝试使用 OleDbCommand 向 Access 数据库 (.accdb) 进行 SQL 查询.

I'm trying to make an SQL query with an OleDbCommand into an Access database (.accdb).

虽然这个命令工作正常(在 OleDbCommand.ExecuteReader() 中):

While this command works fine (in a OleDbCommand.ExecuteReader()):

string command =
   "SELECT cred.* " +
   "FROM TB_CREDENTIALS cred " +
   "INNER JOIN TB_REL_USERS_CREDENTIALS rel ON cred.CRED_ID = rel.REL_USR_CRED_CRED_ID ";

另一个没有，我不明白为什么(我看到的所有示例都使用完全相同的语法):

This other doesn't, and I can't understand why (all examples I see around use the exact same syntax):

string command =
   "SELECT cred.* " +
   "FROM TB_CREDENTIALS cred " +
   "INNER JOIN TB_REL_USERS_CREDENTIALS rel ON cred.CRED_ID = rel.REL_USR_CRED_CRED_ID " +
   "INNER JOIN TB_USERS usr ON usr.USR_ID = rel.REL_USR_CRED_USER_ID ";

给出的异常如下System.Data.OleDb.OleDbException:

查询表达式中的语法错误(缺少运算符)'cred.CRED_ID = rel.REL_USR_CRED_CRED_ID INNER JOIN TB_USERS usr ON usr.USR_ID = rel.REL_USR_CRED_USER_I' (消息在此处剪切)

版本和详细信息:

• 数据库是在 Access 2010 上创建的 .accdb 文件
• 连接是在 C# 中使用 System.Data.OleDb.OleDbConnection
创建的
• 连接提供程序是Microsoft.ACE.OLEDB.12.0"

(这似乎是一个无用的查询，但我当然会添加一个 WHERE usr.SOME_FIELD = some_condition)

(This seems like a useless query, but of course I'll add a WHERE usr.SOME_FIELD = some_condition)

推荐答案

"对于多表连接，您必须将额外的连接嵌套在括号中:"

"For multi-table joins, you have to nest the extra joins in brackets:"

SQL 多连接语句

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