与MySQL选择查询时遇到

Question

我有一个表命名为batch

batch_id  unit_size  product_id 
2    100000   c001 
3    30000   t008 

命名为batch_process

batch_id  process_id  status 
2    100000   0 
2    100000   1 
2    100000   2 
2    100000   1 
3    30000   2 
3    30000   2 
3    30000   2 
3    30000   2 

现在我想输出3 AS batch_id形式batch表，因为在batch_process表中的所有其他表process_id状态为2为batch_id = 3

如何选择它。

Answer 1

这种查询可以帮助你

SELECT batch1.batch_id,batch_process1.process_id 
FROM batch_process AS batch_process1, 
batch AS batch1 
WHERE batch1.batch_id = batch_process1.batch_id 
AND batch_process1.status=2 

Answer 2

如果妳只是想选择BATCH_ID状态为2，那么你可以这样写：

select distinct batch_id from batch_process where status=2 

但如果u想查询从批表信息不只是batch_id，你可以这样写：

SELECT batch.batch_id, 
     batch.unit_size, 
     batch.product_id 
LEFT JOIN batch_process ON batch.batch_id=batch_process.batch_id 
WHERE batch_process.status=2