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Simulate CREATE DATABASE IF NOT EXISTS for PostgreSQL?
...an work around it from within psql by executing the DDL statement conditionally:
SELECT 'CREATE DATABASE mydb'
WHERE NOT EXISTS (SELECT FROM pg_database WHERE datname = 'mydb')\gexec
The manual:
\gexec
Sends the current query buffer to the server, then treats each column of each row of the query's...
General suggestions for debugging in R
...orite debugging routine:
When an error occurs, the first thing that I usually do is look at the stack trace by calling traceback(): that shows you where the error occurred, which is especially useful if you have several nested functions.
Next I will set options(error=recover); this immediately sw...
Why can't I forward-declare a class in a namespace using double colons?
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All other answers were confusing to me but this "you can't declare a class within a namespace from outside that namespace. You have to be in the namespace." was very helpful hint to remember.
– dashesy
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Formatting Decimal places in R
... However, in many domains (e.g., APA style, business reports) formatting requirements dictate that a certain number of decimal places are displayed. This is often done for consistency and standardisation purposes rather than being concerned with significant figures.
Solution:
The following code sh...
Does Java 8 provide a good way to repeat a value or function?
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@jwenting It really depends - typically with GUI stuff (Swing or JavaFX), that removes a lot of boiler plate due to anonymous classes.
– assylias
Aug 30 '13 at 12:12
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内存调试技巧：C 语言最大难点揭秘 - C/C++ - 清泛网 - 专注C/C++及内核技术
...他许多通用语言（如 Java™、Ruby、Haskell、C#、Perl、Smalltalk 等），每种语言都有众多的爱好者和各自的优点。但是，从计算角度来看，每种编程语言优于 C 或 C++ 的主要优点都与便于内存管理密切相关。与内存相关的编程是如...
A type for Date only in C# - why is there no Date type?
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Allow me to add an update to this classic question:
Jon Skeet's Noda Time library is now quite mature, and has a date-only type called LocalDate. (Local in this case just means local to someone, not necessarily local to th...
Getting LaTeX into R Plots
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Here's an example using ggplot2:
q <- qplot(cty, hwy, data = mpg, colour = displ)
q + xlab(expression(beta +frac(miles, gallon)))
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Export database schema into SQL file
... Generate Scripts
When generating the scripts, there is an area that will allow you to script, constraints, keys, etc. From SQL Server 2008 R2 there is an Advanced Option under scripting:
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What is normalized UTF-8 all about?
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Compatibility Normalization
Unicode also includes many characters that really do not belong, but were used in legacy character sets. Unicode added these to allow text in those character sets to be processed as Unicode, and then be converted back without loss.
Compatibility normalization converts t...