如果要与平均查询一起检索平均成绩：
SELECt *FROM ES_TOOL INNER JOIN ES_HARDWARE ON ES_HARDWARE.eshw_ID = ES_TOOL.ESTOOL_HARDWARE INNER JOIN ES_PAYMENT on ES_payment.espay_id = es_TOOL.estool_payment LEFT JOIN ( SELECt b.estch_tool, avg(a.esmrk_value) AvgValue FROM ES_MARK a Inner Join ES_TOOL_CHAPTER b ON a.esmark_tool_chapter = b.estch_id GROUP BY b.estch_tool ) g ON ES_TOOL.ToolColumn = g.estch_tool
用
ToolColumn正确的列名替换。
注意：
SELECT *不建议，请阅读此问题。
