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How to choose the id generation strategy when using JPA and Hibernate
I was going through Id generation section of the Hibernate reference guide and "java persistence with Hibernate"
4 Answers
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@UniqueConstraint and @Column(unique = true) in hibernate annotation
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As said before, @Column(unique = true) is a shortcut to UniqueConstraint when it is only a single field.
From the example you gave, there is a huge difference between both.
@Column(unique = true)
@ManyToOne(optional = false, fet...
How to check if a database exists in SQL Server?
What is the ideal way to check if a database exists on a SQL Server using TSQL? It seems multiple approaches to implement this.
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Multiple Updates in MySQL
...SERT ... ON DUPLICATE KEY UPDATE.
Using your example:
INSERT INTO table (id,Col1,Col2) VALUES (1,1,1),(2,2,3),(3,9,3),(4,10,12)
ON DUPLICATE KEY UPDATE Col1=VALUES(Col1),Col2=VALUES(Col2);
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SQLite table constraint - unique on multiple columns
... adding UNIQUE(i, j) to the create statement is completely ignored on android. It creates the table, but leaves off the UNIQUE constraint. I was only able to do this by using an index.
– gattsbr
Aug 11 at 14:55
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Update a record without first querying?
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can you provide an example?
– Bart Calixto
May 23 '12 at 15:01
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What is “the inverse side of the association” in a bidirectional JPA OneToMany/ManyToOne association
...a foreign key to customer
private Customer customer;
}
The inverse side is the OO "owner" of the object, in this case the customer. The customer has no columns in the table to store the orders, so you must tell it where in the order table it can save this data (which happens via mappedBy).
A...
Sequence contains more than one element
...SingleOrDefault" - from what I can gather the OP is looking for a customer id which (I assume) should be unique, therefore, SingleOrDefault is actually more appropriate than FirstOrDefault. Also, this has actually raised a more serious problem with the OP's database design as it shows that it is pos...
CreateElement with id?
I'm trying to modify this code to also give this div item an ID, however I have not found anything on google, and idName does not work. I read something about append , however it seems pretty complicated for a task that seems pretty simple, so is there an alternative? Thanks :)
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If threads share the same PID, how can they be identified?
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The four threads will have the same PID but only when viewed from above. What you (as a user) call a PID is not what the kernel (looking from below) calls a PID.
In the kernel, each thread has it's own ID, called a PID (although it would possibly make more sens...