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java - MySQLSyntaxErrorException 用于在 MySQL 工作台上正常工作的连接命令

问题描述

String query = "select Books.BookId, Books.Title, Book_Loans.BranchId, count(Book_Loans.BookLoanId) as NoOfCopies from (Book_Loans join Books"
+ "on (Book_Loans.BookId = Books.BookId)) where Books.BookId = ? group by (Book_Loans.BranchId)";
        preparedStatement = connect.prepareStatement(query);
        preparedStatement.setLong(1, bookId);
        resultSet = preparedStatement.executeQuery();
        while(resultSet.next()) {
            System.out.println("BookId:"+resultSet.getLong(1)+"\nTitle:"+resultSet.getString(2)+"\nBranchId:"+resultSet.getLong(3)+"\nNoOfCopies:"+resultSet.getInt(4)+"\n");

我正在尝试执行上面的代码片段，但我得到了 MySQLSyntaxErrorException，如下所示：

Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '(Book_Loans.BookId = Books.BookId)) where Books.BookId = 75 group by (Book_Loans' at line 1
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
    at com.mysql.jdbc.Util.getInstance(Util.java:408)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:944)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3976)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3912)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2530)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2683)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2486)
    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1858)
    at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1966)
    at libraryModel.CopiesCheckedOutFromEachBranchForABook.numberOfCheckedOutCopies(CopiesCheckedOutFromEachBranchForABook.java:36)
    at libraryModel.Main.main(Main.java:47)

与查询相关的表如下： Books( BookId , AuthorName, Title, (Publisher)Name) Book_Loans( BookLoanId , DateOut, DueDate, BranchId, BookId, CardNo)

我试图通过要求用户输入 branchId 来显示从每个分支中签出的书籍的数量。当我在 MySQL 工作台上运行查询时，查询工作正常，但在 Eclipse 上出现语法错误。

标签： javamysqlsqljdbcsyntax-error

解决方案

SQL 查询不正确您必须在 Books 和 on 之间添加一个空格。此外，无需添加额外的括号

利用：

String query = "select Books.BookId, Books.Title, Book_Loans.BranchId, count(Book_Loans.BookLoanId) as NoOfCopies from Book_Loans join Books on Book_Loans.BookId = Books.BookId where Books.BookId = ? group by Book_Loans.BranchId";

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