JOIN A ON B.order_no = A.order_no

This statement is used to join two tables A and B based on the common column "order_no". The resulting table will have all the columns from both tables where the order_no values match.

For example, if table A has columns order_no, customer_name, and order_total, and table B has columns order_no, product_name, and quantity, the resulting table will have columns order_no, customer_name, order_total, product_name, and quantity for all the rows where the order_no values match in both tables.

相关问题

请帮我看看这个sql语句是否正确，并改正：select a.ebeln, a.ebelp, a.art, a.kdauf, a.zbw, a.size1, a.txz01, a.menge, b.quantity, (a.menge - b.quantity) as OWE_MATERIAL, ( select sum(THIS_PLAN_QTY) as HAVE_PLAN , a.ebeln , a.ebelp , a.kdauf from SCM_OUTSOURCE_PRODUCTION_PLAN_LIST c , SCM_PROCESS_PURCHASE_ORDER_D a group by c.order_no , c.order_seq , c.sales_order , a.ebeln , a.ebelp , a.kdauf having c.order_no = a.ebeln And c.order_seq = a.ebelp And c.sales_order = a.kdauf ) , ( select a.menge - t.HAVE_PLAN as OWN_PLAY from (select sum(THIS_PLAN_QTY) as HAVE_PLAN , c.order_no , c.order_seq , c.sales_order from SCM_OUTSOURCE_PRODUCTION_PLAN_LIST c , SCM_PROCESS_PURCHASE_ORDER_D a group by c.order_no , c.order_seq , c.sales_order , a.ebeln , a.ebelp , a.kdauf having c.order_no = a.ebeln And c.order_seq = a.ebelp And c.sales_order = a.kdauf ) t , SCM_PROCESS_PURCHASE_ORDER_D a where a.ebeln = t.order_no and a.ebelp = t.order_seq and a.menge = t.sales_order ) , d.scan_qty, (d.quantity - d.scan_qty) as OWN_PRODUCE, e.scan_qty, (e.quantity - e.scan_qty) as OWE_SHIP from SCM_PROCESS_PURCHASE_ORDER_D a left join MMS_INOUT_BILL_M b On a.ebeln = b.purchase_order_number And a.ebelp = b.purchase_order_seq And a.kdauf = b.sales_order left join SCM_OUTSOURCE_PRODUCTION_PLAN_LIST c on a.ebeln = c.order_no And a.ebelp = c.order_seq And a.kdauf = c.sales_order left join SCM_PROCESS_OUTPUT d on a.ebeln = d.order_no And a.ebelp = d.order_seq And a.kdauf = d.sales_order left join SCM_OUTSOURCE_SHIP e on a.ebeln = e.qr_code and a.ebelp = e.order_no and a.kdauf = e.order_seq where a.art = 'IE7181' Order by a.ebeln desc, a.ebelp;

这个 SQL 语句比较复杂，但是有一些问题需要修改：

- 在子查询中，需要将 select 子句中的 a.ebeln, a.ebelp, a.kdauf 与 group by 子句中的字段保持一致，否则会出现错误。
- 子查询中的第一个 SELECT 子句需要加上 WHERE 子句，限制查询条件。
- 子查询中的第二个 SELECT 子句中的 a.menge 应该改为 t.sales_order。
- 在最后的 SELECT 子句中，d.scan_qty 与 e.scan_qty 都没有明确指定表名，可能会出现错误。

以下是修改后的 SQL 语句：

SELECT
    a.ebeln,
    a.ebelp,
    a.art,
    a.kdauf,
    a.zbw,
    a.size1,
    a.txz01,
    a.menge,
    b.quantity,
    (a.menge - b.quantity) AS OWE_MATERIAL,
    (
        SELECT
            SUM(c.THIS_PLAN_QTY) AS HAVE_PLAN,
            a.ebeln,
            a.ebelp,
            a.kdauf
        FROM
            SCM_OUTSOURCE_PRODUCTION_PLAN_LIST c,
            SCM_PROCESS_PURCHASE_ORDER_D a
        WHERE
            c.order_no = a.ebeln
            AND c.order_seq = a.ebelp
            AND c.sales_order = a.kdauf
            AND a.art = 'IE7181'
        GROUP BY
            c.order_no,
            c.order_seq,
            c.sales_order,
            a.ebeln,
            a.ebelp,
            a.kdauf
    ),
    (
        SELECT
            a.menge - t.sales_order AS OWN_PLAY
        FROM
            (
                SELECT
                    SUM(c.THIS_PLAN_QTY) AS HAVE_PLAN,
                    c.order_no,
                    c.order_seq,
                    c.sales_order
                FROM
                    SCM_OUTSOURCE_PRODUCTION_PLAN_LIST c,
                    SCM_PROCESS_PURCHASE_ORDER_D a
                WHERE
                    c.order_no = a.ebeln
                    AND c.order_seq = a.ebelp
                    AND c.sales_order = a.kdauf
                    AND a.art = 'IE7181'
                GROUP BY
                    c.order_no,
                    c.order_seq,
                    c.sales_order,
                    a.ebeln,
                    a.ebelp,
                    a.kdauf
            ) t,
            SCM_PROCESS_PURCHASE_ORDER_D a
        WHERE
            a.ebeln = t.order_no
            AND a.ebelp = t.order_seq
            AND a.kdauf = t.sales_order
            AND a.art = 'IE7181'
    ),
    d.scan_qty,
    (d.quantity - d.scan_qty) AS OWN_PRODUCE,
    e.scan_qty,
    (e.quantity - e.scan_qty) AS OWE_SHIP
FROM
    SCM_PROCESS_PURCHASE_ORDER_D a
LEFT JOIN MMS_INOUT_BILL_M b ON a.ebeln = b.purchase_order_number AND a.ebelp = b.purchase_order_seq AND a.kdauf = b.sales_order
LEFT JOIN SCM_OUTSOURCE_PRODUCTION_PLAN_LIST c ON a.ebeln = c.order_no AND a.ebelp = c.order_seq AND a.kdauf = c.sales_order
LEFT JOIN SCM_PROCESS_OUTPUT d ON a.ebeln = d.order_no AND a.ebelp = d.order_seq AND a.kdauf = d.sales_order
LEFT JOIN SCM_OUTSOURCE_SHIP e ON a.ebeln = e.qr_code AND a.ebelp = e.order_no AND a.kdauf = e.order_seq
WHERE
    a.art = 'IE7181'
ORDER BY
    a.ebeln DESC,
    a.ebelp;

select count(*) from outward_delivery_order odo left join mc_order mo on mo.id = odo.order_id left join starbucks_order so on so.order_no = odo.order_no; 优化这段sql

对于这段 SQL 查询，你可以尝试以下优化方法：

1. 添加索引：确保相应的表上的列都有适当的索引。对于 `outward_delivery_order` 表，确保 `order_id` 列有索引；对于 `mc_order` 表，确保 `id` 列有索引；对于 `starbucks_order` 表，确保 `order_no` 列有索引。这将加快连接操作和查询速度。

2. 避免使用通配符：使用具体的列名代替 `*`，这样可以减少从磁盘读取的数据量。

3. 调整连接顺序：根据表的大小和关联关系，调整连接的顺序，将最小的表放在前面。这可以减少连接操作的数据量。

4. 考虑使用内连接：如果只需要返回存在关联的记录，可以将左连接改为内连接（INNER JOIN），这样可以进一步减少数据量。

优化后的 SQL 查询如下所示：

SELECT COUNT(*)
FROM outward_delivery_order odo
INNER JOIN mc_order mo ON mo.id = odo.order_id
INNER JOIN starbucks_order so ON so.order_no = odo.order_no;

请注意，具体的优化方法可能因数据库引擎、表结构和数据量的差异而有所不同。在进行任何更改之前，请确保在适当的环境中进行测试和备份数据。