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What is a proper naming convention for MySQL FKs?
...le name]_[referencing field name]
Example:
CREATE TABLE users(
user_id int,
name varchar(100)
);
CREATE TABLE messages(
message_id int,
user_id int
);
ALTER TABLE messages ADD CONSTRAINT fk_messages_users_user_id
FOREIGN KEY (user_id) REFERENCES users(user_id);
...
Delete duplicate records in SQL Server?
Consider a column named EmployeeName table Employee . The goal is to delete repeated records, based on the EmployeeName field.
...
Difference Between One-to-Many, Many-to-One and Many-to-Many?
... One Person Has Many Skills, a Skill is not reused between Person(s)
Unidirectional: A Person can directly reference Skills via its Set
Bidirectional: Each "child" Skill has a single pointer back up to the
Person (which is not shown in your code)
Many-to-Many: One Person Has Many Skil...
Distributed sequence number generation?
...ing now.
You'll need to differentiate between sequence numbers and unique IDs that are (optionally) loosely sortable by a specific criteria (typically generation time). True sequence numbers imply knowledge of what all other workers have done, and as such require shared state. There is no easy way ...
Exposing database IDs - security risk?
I've heard that exposing database IDs (in URLs, for example) is a security risk, but I'm having trouble understanding why.
...
How do I find a stored procedure containing ?
...TION LIKE '%Foo%'
AND ROUTINE_TYPE='PROCEDURE'
SELECT OBJECT_NAME(id)
FROM SYSCOMMENTS
WHERE [text] LIKE '%Foo%'
AND OBJECTPROPERTY(id, 'IsProcedure') = 1
GROUP BY OBJECT_NAME(id)
SELECT OBJECT_NAME(object_id)
FROM sys.sql_modules
WHERE OBJECTPROPERTY(object_...
How to create a Custom Dialog box in android?
...l
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="80dp"
android:background="#3E80B4"
android:orientation="vertical" >
<TextView
androi...
How to delete from select in MySQL?
...ner subquery result (looks rather hacky, though):
DELETE FROM posts WHERE id IN (
SELECT * FROM (
SELECT id FROM posts GROUP BY id HAVING ( COUNT(id) > 1 )
) AS p
)
Or use joins as suggested by Mchl.
sh...
How do I perform the SQL Join equivalent in MongoDB?
... The new $lookup operator added to the aggregation pipeline is essentially identical to a left outer join:
https://docs.mongodb.org/master/reference/operator/aggregation/lookup/#pipe._S_lookup
From the docs:
{
$lookup:
{
from: <collection to join>,
localField: <fiel...
How to annotate MYSQL autoincrement field with JPA annotations
...
To use a MySQL AUTO_INCREMENT column, you are supposed to use an IDENTITY strategy:
@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
private Long id;
Which is what you'd get when using AUTO with MySQL:
@Id @GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
Which is a...