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Calculate a Running Total in SQL Server
Imagine the following table (called TestTable ):
15 Answers
15
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SQL variable to hold list of integers
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Table variable
declare @listOfIDs table (id int);
insert @listOfIDs(id) values(1),(2),(3);
select *
from TabA
where TabA.ID in (select id from @listOfIDs)
or
declare @listOfIDs varchar(1000);
SET @listOfIDs = ',1,2,3...
Counting null and non-null values in a single query
I have a table
26 Answers
26
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SQL ON DELETE CASCADE, Which Way Does the Deletion Occur?
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Cascade will work when you delete something on table Courses. Any record on table BookCourses that has reference to table Courses will be deleted automatically.
But when you try to delete on table BookCourses only the table itself is affected and not on the Courses
foll...
SQL Server query to find all permissions/access for all users in a database
...have access to a specific database, or objects within the database such as tables, views, and stored procedures, either directly or due to roles, etc. This report would be used for security auditing purposes. Not sure if anyone has a query that will fit my needs completely, but hopefully something...
Why should hash functions use a prime number modulus?
A long time ago, I bought a data structures book off the bargain table for $1.25. In it, the explanation for a hashing function said that it should ultimately mod by a prime number because of "the nature of math".
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select into in mysql
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Use the CREATE TABLE SELECT syntax.
http://dev.mysql.com/doc/refman/5.0/en/create-table-select.html
CREATE TABLE new_tbl SELECT * FROM orig_tbl;
share
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MySQL主从服务器数据一致性的核对与修复 - 数据库(内核) - 清泛网 - 专注C/...
...一天被掩盖的问题会再次爆发出来。
Percona Toolkit里的pt-table-checksum和pt-table-sync可以搞定此类问题。它们的安装很简单，可以依照自己的操作系统选择下载rpm或者deb软件包来安装，当然也可以使用源代码来安装，不过要注意的是...
CHECK constraint in MySQL is not working
First I created a table like
8 Answers
8
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Numbering rows within groups in a data frame
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Use ave, ddply, dplyr or data.table:
df$num <- ave(df$val, df$cat, FUN = seq_along)
or:
library(plyr)
ddply(df, .(cat), mutate, id = seq_along(val))
or:
library(dplyr)
df %>% group_by(cat) %>% mutate(id = row_number())
or (the most memor...