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What's the best practice for primary keys in tables?
When designing tables, I've developed a habit of having one column that is unique and that I make the primary key. This is achieved in three ways depending on requirements:
...
How to vertically center content with variable height within a div?
...ra markup and seems to work extremely well. I couldn’t use the display: table method because table elements don’t obey the max-height property.
.block {
height: 300px;
text-align: center;
background: #c0c0c0;
border: #a0a0a0 solid 1px;
margin: 20px;
}
.block::before {
...
What is the significance of load factor in HashMap?
...apacity and load factor. The capacity is the number of buckets in the hash table, and the initial capacity is simply the capacity at the time the hash table is created. The load factor is a measure of how full the hash table is allowed to get before its capacity is automatically increased. When the ...
How to UPSERT (MERGE, INSERT … ON DUPLICATE UPDATE) in PostgreSQL?
...ions:
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 concurrently trying to perform inserts.
The PostgreSQL documentation co...
When to add what indexes in a table in Rails
... end of the index.
If you have a has_many :through relationship, your join table should have a unique index on both properties involved in the join as a compound key.
If you fetch a record directly using a unique identifier such as username or email, that should be a unique index.
If you fetch sets ...
NHibernate vs LINQ to SQL
...
LINQ to SQL forces you to use the table-per-class pattern. The benefits of using this pattern are that it's quick and easy to implement and it takes very little effort to get your domain running based on an existing database structure. For simple applicatio...
Count the number of occurrences of a string in a VARCHAR field?
I have a table like this:
7 Answers
7
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When is SQLiteOpenHelper onCreate() / onUpgrade() run?
I have created my tables in my SQLiteOpenHelper onCreate() but receive
15 Answers
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How to disable scrolling in UITableView table when the content fits on the screen
I have a few (grouped style) tables in my iphone app (only on part of the screen and added with Interface Builder though, not subclassed from UITableViewController ) that 80% of the time are small and will fit on the screen. When the table fits on the screen, I'd like to disable scrolling, to ma...
Relational Database Design Patterns? [closed]
...elationships using a foreign key.
Many-to-Many relationships with a bridge table.
Optional one-to-one relationships managed with NULLs in the FK column.
Star-Schema: Dimension and Fact, OLAP design.
Fully normalized OLTP design.
Multiple indexed search columns in a dimension.
"Lookup table" that con...