Question

我有8个主表，每个表有大约60万条记录。

我们说表名是

type_11_14 
type_12_15
type_13_16
type_4_5
type_6
type_7
type_8
type_10

每个表都有代码和名称列。代码是主键。我无法组合所有这些表并制作一个表。

在上表中， type_11_14 包含类型11和14条记录 type_7 有7类记录

我有其他表 all_types_count 。它具有上述类型的计数信息。对于给定的类型和代码列表（我们给出的最大代码为50），我需要获取其名称，类型，代码和计数

我用UNION编写了以下查询。查询运行正常。但如果我运行解释计划，我会得到

错误无法启用约束。一行或多行包含违反非空，唯一或外键约束的值。

再次在下面的查询中我查询 all_types_count 表8次。而不是我想到从 all_types_count 首先获取所有记录，然后离开加入主表以获得所需的结果..

不确定什么是最好的SQL查询解决方案。有人可以为我提供最好的方法吗？

SELECT type,code,total_count,type_11_14.name 
FROM all_types_count,type_11_14 
WHERE all_types_count.type in (11,14) 
AND all_types_count.code=type_11_14.code 
AND all_types_count.code in ( 3456,6789)

UNION ALL

SELECT type,code,total_count,type_12_15.name 
FROM all_types_count,type_12_15 
WHERE all_types_count.type in (12,15) 
AND all_types_count.code=type_12_15.code 
AND all_types_count.code in ( 2345,9087,234)

UNION ALL

SELECT type,code,total_count,type_13_16.name 
FROM all_types_count,type_13_16 
WHERE all_types_count.type in (13,16) 
AND all_types_count.code=type_13_16.code 
AND all_types_count.code in ( 98,24)

UNION ALL

SELECT type,code,total_count,type_4_5.name 
FROM all_types_count,type_4_5 
WHERE all_types_count.type in (4,5) 
AND all_types_count.code=type_4_5.code  
AND all_types_count.code in ( 765,9087,3456)

UNION ALL

SELECT type,code,total_count,type_6.name 
FROM all_types_count,type_6 
WHERE all_types_count.type=6 
AND all_types_count.code=type_6.code  
AND all_types_count.code in ( 5563,323,434,3442)

UNION ALL

SELECT type,code,total_count,type_7.name 
FROM all_types_count,type_7 
WHERE all_types_count.type=7 
AND all_types_count.code=type_7.code  
AND all_types_count.code in ( 7887,313,23,32,21)

UNION ALL

SELECT type,code,total_count,type_8.name 
FROM all_types_count,type_8 
WHERE all_types_count.type=8 
AND all_types_count.code=type_8.code  
AND all_types_count.code in ( 9988,1221)

UNION ALL

SELECT type,code,total_count,type_10.name 
FROM all_types_count,type_10 
WHERE all_types_count.type=10 
AND all_types_count.code=type_10.code  
AND all_types_count.code in ( 7787,23213)

谢谢

基兰

Answer 1

如果您的查询被写为：

，那么查询应该更有效率

SELECT type,code,total_count,type_11_14.name 
FROM all_types_count 
left outer join type_11_14 
     on all_types_count.type in (11,14) 
     and all_types_count.code=type_11_14.code 
     and all_types_count.code in ( 3456,6789) 
left outer join type_12_15 
     on all_types_count.type in (12,15) 
     and all_types_count.code=type_12_15.code 
     and all_types_count.code in ( 2345,9087,234) 
left outer join  . . .

如果您不熟悉连接/左外连接/右外连接/交叉连接语法，那么您应该学习它。

在原始查询中，优化器很可能会为每个子查询读取一次all_types_count表。使用联接，它应该只读取一次，在需要时加入其他表。

加入更多父表

1 个答案: