Question

我在php（mysql）中生成一个报告，

例如：

`select count(id) as tot_user from user_table
 select count(id) as tot_cat from cat_table
 select count(id) as tot_course from course_table`

像这样我有12张桌子。

我可以在单个查询中制作它吗？如果我做了？流程变得缓慢？

Answer 1

SELECT  (
    SELECT COUNT(*)
    FROM   user_table
    ) AS tot_user,
    (
    SELECT COUNT(*)
    FROM   cat_table
    ) AS tot_cat,
    (
    SELECT COUNT(*)
    FROM   course_table
    ) AS tot_course

Answer 2

如果使用MyISAM表，最快的方法是直接查询统计数据：

select table_name, table_rows 
     from information_schema.tables 
where 
     table_schema='databasename' and 
     table_name in ('user_table','cat_table','course_table')

如果您有InnoDB，则必须使用count（）进行查询，因为information_schema.tables中的报告值是错误的。

Answer 3

你当然可以使用Ben James所假设的Select Agregation语句，但是这会产生一个包含尽可能多的列的视图。另一种方法可能如下：

SELECT COUNT(user_table.id) AS TableCount,'user_table' AS TableSource FROM user_table
UNION SELECT COUNT(cat_table.id) AS TableCount,'cat_table' AS TableSource FROM cat_table
UNION SELECT COUNT(course_table.id) AS TableCount, 'course_table' AS TableSource From course_table;

关于像这样的approch的好处是你可以显式编写Union语句并生成一个视图或创建一个临时表来保存从Proc cals使用变量代替你的表名连续添加的值。我倾向于更多地使用后者，但这实际上取决于个人偏好和应用。如果您确定表永远不会更改，那么您希望数据采用单行格式，并且您不会添加表。坚持Ben James的解决方案。否则我会建议灵活性，你总是可以破解交叉表结构。

Answer 4

select RTRIM(A.FIELD) from SCHEMA.TABLE A where RTRIM(A.FIELD) =  ('10544175A') 
 UNION  
select RTRIM(A.FIELD) from SCHEMA.TABLE A where RTRIM(A.FIELD) = ('10328189B') 
 UNION  
select RTRIM(A.FIELD) from SCHEMA.TABLE A where RTRIM(A.FIELD) = ('103498732H')

Answer 5

我知道这是一个旧堆栈，但是我将发布此Multi-SQL select案例

    SELECT bp.bizid, bp.usrid, bp.website, 
ROUND((SELECT SUM(rating) FROM ratings WHERE bizid=bp.bizid)/(SELECT COUNT(*) FROM ratings WHERE bizid=bp.bizid), 1) AS 'ratings', 
(SELECT COUNT(*) FROM bzreviews WHERE bizid=bp.bizid) AS 'ttlreviews', 
bp.phoneno, als.bizname, 
(SELECT COUNT(*) FROM endorsment WHERE bizid=bp.bizid) AS 'endorses'
, als.imgname, bp.`location`, bp.`ownership`, 
(SELECT COUNT(*) FROM follows WHERE bizid=bp.bizid) AS 'followers', 
bp.categories, bp.openhours, bp.bizdecri FROM bizprofile AS bp 
INNER JOIN alluser AS als ON bp.usrid=als.userid 
WHERE als.usertype='Business'

Answer 6

SELECT t1.credit, 
       t2.debit 
FROM   (SELECT Sum(c.total_amount) AS credit 
        FROM   credit c 
        WHERE  c.status = "a") AS t1, 
       (SELECT Sum(d.total_amount) AS debit 
        FROM   debit d 
        WHERE  d.status = "a") AS t2

单个查询中的多个select语句

6 个答案: