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SQL: How to properly check if a record exists
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It's better to use either of the following:
-- Method 1.
SELECT 1
FROM table_name
WHERE unique_key = value;
-- Method 2.
SELECT COUNT(1)
FROM table_name
WHERE unique_key = value;
The first alternative should give you no result or one result, the second count should be zero or...
How to convert 1 to true or 0 to false upon model fetch
...th true or false into a boolean/tinyint field in the database, which uses 1 or 0 .
4 Answers
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What is the ultimate postal code and zip regex?
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132
There is none.
Postal/zip codes around the world don't follow a common pattern. In some count...
Difference between Divide and Conquer Algo and Dynamic Programming
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158
Divide and Conquer
Divide and Conquer works by dividing the problem into sub-problems, conque...
Fastest way to check if a string matches a regexp in ruby?
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104
Starting with Ruby 2.4.0, you may use RegExp#match?:
pattern.match?(string)
Regexp#match? i...
Find XOR of all numbers in a given range
...u are given a large range [a,b] where 'a' and 'b' can be typically between 1 and 4,000,000,000 inclusive. You have to find out the XOR of all the numbers in the given range.
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Implement Stack using Two Queues
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194
Version A (efficient push):
push:
enqueue in queue1
pop:
while size of queue1 is bigge...
Regex group capture in R with multiple capture-groups
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118
str_match(), from the stringr package, will do this. It returns a character matrix with one co...
How to detect my browser version and operating system using JavaScript?
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10 Answers
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