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SQL: How to properly check if a record exists
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I would prefer not use Count function at all:
IF [NOT] EXISTS ( SELECT 1 FROM MyTable WHERE ... )
<do smth>
For example if you want to check if user exists before inserting it into the database the query can look like this:
IF NOT EXISTS ( SELECT 1 ...
How do I revert all local changes in Git managed project to previous state?
...to the index (i.e., that you have added), do this. Warning this will reset all of your unpushed commits to master!:
git reset
If you want to revert a change that you have committed, do this:
git revert <commit 1> <commit 2>
If you want to remove untracked files (e.g., new files, ge...
Laravel - Eloquent or Fluent random row
...domOrder()->first();
or using the random method for collections:
User::all()->random();
User::all()->random(10); // The amount of items you wish to receive
Laravel 4.2.7 - 5.1:
User::orderByRaw("RAND()")->get();
Laravel 4.0 - 4.2.6:
User::orderBy(DB::raw('RAND()'))->get();
Laravel...
LINQ to Entities does not recognize the method 'System.String ToString()' method, and this method ca
... select p;
The problem arises because ToString() isn't really executed, it is turned into a MethodGroup and then parsed and translated to SQL. Since there is no ToString() equivalent, the expression fails.
Note:
Make sure you also check out Alex's answer regarding the SqlFunction...
What is the difference between a Docker image and a container?
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An instance of an image is called a container. You have an image, which is a set of layers as you describe. If you start this image, you have a running container of this image. You can have many running containers of the same image.
You can see all you...
How to get duplicate items from a list using LINQ? [duplicate]
...t; s)
.SelectMany(grp => grp.Skip(1));
Note that this will return all duplicates, so if you only want to know which items are duplicated in the source list, you could apply Distinct to the resulting sequence or use the solution given by Mark Byers.
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Algorithms based on number base systems? [closed]
...ctional Data Structures that discusses "Numerical Representations": essentially, take some representation of a number and convert it into a data structure. To give a flavor, here are the sections of that chapter:
Positional Number Systems
Binary Numbers (Binary Random-Access Lists, Zeroless Repres...
Retrieving the inherited attribute names/values using Java Reflection
...bj' which is extended from 'ParentObj'. Now, if it is possible to retrieve all the attribute names and values of ChildObj, including the inherited attributes too, using Java reflection mechanism?
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Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign
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This problem is usually caused by one of the following
null values being returned for columns not set to AllowDBNull
duplicate rows being returned with the same primary key.
a mismatch in column definition (e.g. size of char fields) between t...
Get all table names of a particular database by SQL query?
... Server and MySQL 2) INFORMATION_SCHEMA.TABLES exists only in MySQL 3) I really wonder how comes you got so many upvotes for this ...
– Apostolos
Dec 14 '18 at 11:04
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