Question

我在mysql.connector中发现了一些非常奇怪的行为。具有三个内部联接的SQL查询返回一个空集，但是两个内部联接返回正确的结果。

query = 'select * from `ont_system` inner join compounds_crude ON(compounds_crude.id=compound_id) inner join crude2chebi on(compounds_crude.id=crude_id) inner join tc2acc on (ont_system.tcid=tc2acc.tcid) where crude2chebi.approved=1 limit 10;'

此代码将返回一个空集。但是，如果删除最后一个INNER JOIN，则将在python中得到结果。修改后的查询为：

query = 'select * from `ont_system` inner join compounds_crude ON(compounds_crude.id=compound_id) inner join crude2chebi on(compounds_crude.id=crude_id) inner join tc2acc on (ont_system.tcid=tc2acc.tcid) where crude2chebi.approved=1 limit 10;'

但是，两个查询都在MySQL Shell中工作。最后一个破坏python的内部联接是什么？这是我的python代码：

    import cgitb
    import cgi
    import mysql.connector
    import collections
    cnx = mysql.connector.connect(user='x', password='x',
                                  host='127.0.0.1',
                                  database='x')
    cursor = cnx.cursor()

    Assignment = collections.namedtuple('Assignment',['chebi_id','tcid','acc'])

    def loadItems():
        query = 'select * from `ont_system` inner join compounds_crude ON(compounds_crude.id=compound_id) inner join crude2chebi on(compounds_crude.id=crude_id) inner join tc2acc on (ont_system.tcid=tc2acc.tcid) where crude2chebi.approved=1 limit 10;'
        # This query will make some redundancies, since there may be several acc's per TCID
        cursor.execute(query)
        print cursor.fetchall()


    if __name__=='__main__':
        loadItems()

mysql.connector模块因3个或更多内部联接而失败

0 个答案: