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How to filter SQL results in a has-many-through relation
Assuming I have the tables student , club , and student_club :
13 Answers
13
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Good way to use table alias in Update statement?
I'm using SQL Server, and trying to update rows from within the same table. I want to use a table alias for readability.
2 ...
URL Encoding using C#
...asy.
As for Linux versus windows, there are some characters that are acceptable in Linux that are not in Windows, but I would not worry about that, as the folder name can be returned by decoding the Url string, using UrlDecode, so you can round trip the changes.
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Finding duplicate values in MySQL
I have a table with a varchar column, and I would like to find all the records that have duplicate values in this column. What is the best query I can use to find the duplicates?
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How to implement a Map with multiple keys? [duplicate]
...nother solution is to use Google's Guava
import com.google.common.collect.Table;
import com.google.common.collect.HashBasedTable;
Table<String, String, Integer> table = HashBasedTable.create();
The usage is really simple:
String row = "a";
String column = "b";
int value = 1;
if (!table.c...
Whether a variable is undefined [duplicate]
....page_name ? "&page_name=" + opt.page_name : "");
retval.push( opt.table_name ? "&table_name=" + opt.table_name : "");
retval.push( opt.optionResult ? "&optionResult=" + opt.optionResult : "");
return retval.join("");
}
my_url("?z=z", { page_name : "pageX" /* no table_name ...
How to reshape data from long to wide format
...
Another option if performance is a concern is to use data.table's extension of reshape2's melt & dcast functions
(Reference: Efficient reshaping using data.tables)
library(data.table)
setDT(dat1)
dcast(dat1, name ~ numbers, value.var = "value")
# name 1 ...
Postgres: How to do Composite keys?
... error, and omit the redundant CONSTRAINT (already implied), too:
CREATE TABLE tags
(
question_id INTEGER NOT NULL,
tag_id SERIAL NOT NULL,
tag1 VARCHAR(20),
tag2 VARCHAR(20),
tag3 VARCHAR(20),
PRIMARY ...
How do you use script variables in psql?
...nd can then be substituted, for example, as ...
SELECT * FROM :myvariable.table1;
... or ...
SELECT * FROM table1 WHERE :myvariable IS NULL;
edit: As of psql 9.1, variables can be expanded in quotes as in:
\set myvariable value
SELECT * FROM table1 WHERE column1 = :'myvariable';
In olde...
How do you debug MySQL stored procedures?
...current process for debugging stored procedures is very simple. I create a table called "debug" where I insert variable values from the stored procedure as it runs. This allows me to see the value of any variable at a given point in the script, but is there a better way to debug MySQL stored procedu...