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How can you represent inheritance in a database?
...--+---------------------+----------+----------------+------------------+
| id | date_issued | type | vehicle_reg_no | property_address |
+------+---------------------+----------+----------------+------------------+
| 1 | 2010-08-20 12:00:00 | MOTOR | 01-A-04004 | NULL ...
Best Practice: Access form elements by HTML id or name attribute?
...
Give your form an id only, and your input a name only:
<form id="myform">
<input type="text" name="foo">
Then the most standards-compliant and least problematic way to access your input element is via:
document.getElementById...
SQL RANK() versus ROW_NUMBER()
...bout the differences between these. Running the following SQL gets me two idential result sets. Can someone please explain the differences?
...
Jdbctemplate query for string: EmptyResultDataAccessException: Incorrect result size: expected 1, ac
...n I just ask why 'Now the correct way is not to catch this exception', considering if you're using queryForObject? What would be wrong with catching an exception in the case of queryForObject? Thanks :)
– Michael Stokes
Dec 12 '16 at 3:49
...
Trigger a button click with JavaScript on the Enter key in a text box
...t to trigger the button's click event when the Enter key is pressed inside the text box?
30 Answers
...
Drop a temporary table if it exists
... IF EXISTS ##CLIENTS_KEYWORD
On previous versions you can use
IF OBJECT_ID('tempdb..##CLIENTS_KEYWORD', 'U') IS NOT NULL
/*Then it exists*/
DROP TABLE ##CLIENTS_KEYWORD
CREATE TABLE ##CLIENTS_KEYWORD
(
client_id INT
)
You could also consider truncating the table instead rather than dropping ...
how to add records to has_many :through association in rails
...mer.new(params[:customer])
@cust.houses << House.find(params[:house_id])
Or when creating a new house for a customer:
@cust = Customer.new(params[:customer])
@cust.houses.create(params[:house])
You can also add via ids:
@cust.house_ids << House.find(params[:house_id])
...
Rails raw SQL example
...
side note: records_array will be of different types for different database adapters. If you're using PG, it will be an instance of PG::Result, not Array.
– tybro0103
Jan 14 '14 at 17:28
...
Remove Primary Key in MySQL
...erty before dropping the key:
ALTER TABLE user_customer_permission MODIFY id INT NOT NULL;
ALTER TABLE user_customer_permission DROP PRIMARY KEY;
Note that you have a composite PRIMARY KEY which covers all three columns and id is not guaranteed to be unique.
If it happens to be unique, you can m...
How to UPSERT (MERGE, INSERT … ON DUPLICATE UPDATE) in PostgreSQL?
...em in useful detail.
In general you must choose between two options:
Individual insert/update operations in a retry loop; or
Locking the table and doing batch merge
Individual row retry loop
Using individual row upserts in a retry loop is the reasonable option if you want many connections concurre...