[英]Using SubQuery as Field Column
我有将子查询作为字段列的查询,但我想在其他地方使用此字段列。
SELECT c.country_code AS
country_code,
c.dial_code AS
dial_code,
(SELECT r.destination
FROM region r
WHERE r.country_code = c.country_code
AND r.dial_code = c.dial_code) AS
destination,
c.start_time,
c.duration,
c.call_type,
c.customer_prefix AS
customer_prefix,
c.vendor_prefix AS
vendor_prefix,
(SELECT Round(r.rate, 3)
FROM rate r
INNER JOIN region re
ON r.region_id = re.id
INNER JOIN account_prefix ap
ON r.account_prefix_id = ap.id
WHERE re.country_code = c.country_code
AND re.dial_code = c.dial_code
AND ap.prefix = c.customer_prefix
AND ap.prefix_type = 0) AS
**customer_rate**,
(SELECT Round(r.rate, 3)
FROM rate r
INNER JOIN region re
ON r.region_id = re.id
INNER JOIN account_prefix ap
ON r.account_prefix_id = ap.id
WHERE re.country_code = c.country_code
AND re.dial_code = c.dial_code
AND ap.prefix = c.vendor_prefix
AND ap.prefix_type = 1) AS
**vendor_rate**,
(SELECT Round(r.rate, 3)
FROM rate r
INNER JOIN region re
ON r.region_id = re.id
INNER JOIN account_prefix ap
ON r.account_prefix_id = ap.id
WHERE re.country_code = c.country_code
AND re.dial_code = c.dial_code
AND ap.prefix = c.customer_prefix
AND ap.prefix_type = 0) - (SELECT Round(r.rate, 3)
FROM rate r
INNER JOIN region re
ON r.region_id = re.id
INNER JOIN account_prefix ap
ON r.account_prefix_id
= ap.id
WHERE
re.country_code = c.country_code
AND re.dial_code = c.dial_code
AND ap.prefix = c.vendor_prefix
AND ap.prefix_type = 1) AS **unit_profit**,
unit_profit * duration
FROM cdr c
LIMIT 100;
如您所见,我想使用 unit_profit、customer_rate 和 vendor_rate。 如何实现?
编辑:
任何显示加入视图的教程?
您需要做的是获取所有在苍蝇内部完成的子查询,并创建与 CDR 表的连接。
这将大大提高查询的性能和响应时间。 您现在所做的是对 CDR 中的每个记录执行 3 个查询。 如果这个表(CDR)只有几条记录是可以的,但如果没有,这可能会消耗大量的处理器、内存和磁盘 I/O。
执行“加入”并以相同格式显示信息的技巧是加入 3 次相同的子查询,但使用不同的别名。
select c.country_code, customer_rate_table.customer_rate
from CDR c
left outer join on ( SELECT Round(r.rate, 3) customer_rate , re.country_code,
re.dial_code, re.dial_code, ap.prefix
FROM rate r
INNER JOIN region re
ON r.region_id = re.id
INNER JOIN account_prefix ap
ON r.account_prefix_id = ap.id
WHERE ap.prefix_type = 1
) customer_rate_table
ON customer_rate.country_code = c.country_code
AND customer_rate.dial_code = c.dial_code
AND customer_rate.prefix = c. customer_prefix
left outer join on ( {Same as above but with the right fields} ) vendor_rate_table
ON vendor_rate_table.country_code = c.country_code
AND vendor_rate_table.dial_code = c.dial_code
AND vendor_rate_table.prefix = c.vendor_prefix
然后下一张桌子...
这段代码并不完整,但我认为可以解释您需要做什么。
谢谢!
@leo
在性能方面,像您在查询中拥有的相关子查询通常很糟糕。 由于您只检索 100 行,因此应该不会太糟糕,但如果您希望它更快,则必须重写您的查询。
手头的问题可以通过以下方式轻松解决:
SELECT *, unit_profit * duration AS my_calc
FROM (
-- your query here
-- just without "unit_profit * duration"
-- and maybe without redundant column aliases
) AS sub
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