大约有 37,000 项符合查询结果（耗时：0.0212秒） [XML]
How can I make a JPA OneToOne relation lazy
... a proxy object or NULL and it can't determine that by looking at its base table's columns due to one-to-one normally being mapped via shared PK, so it has to be eagerly fetched anyway making proxy pointless. Here's a more detailed explanation.
many-to-one associations (and one-to-many, obviously) d...
Surrogate vs. natural/business keys [closed]
...lled as such. It is nothing more than a NOT NULL UNIQUE constraint, and a table can have more than one.
If you use a surrogate key, you still want a business key to ensure uniqueness according to the business rules.
share
...
How important is the order of columns in indexes?
...index pages that the optimiser must scan; this can be significant in large tables with millions of rows
– Paul Hatcher
Oct 28 '16 at 14:58
|
...
How can I check MySQL engine type for a specific table?
My MySQL database contains several tables using different storage engines
(specifically myisam and innodb). How can I find out which tables are
using which engine?
...
On delete cascade with doctrine2
... make a simple example in order to learn how to delete a row from a parent table and automatically delete the matching rows in the child table using Doctrine2.
...
How do I vertically align text in a div?
...solution.html
Article summary:
For a CSS 2 browser, one can use display:table/display:table-cell to center content.
A sample is also available at JSFiddle:
div { border:1px solid green;}
<div style="display: table; height: 400px; overflow: hidden;">
<div style="display: table-c...
Printing Lists as Tabular Data
...e 24
Bob 19
tabulate has many options to specify headers and table format.
print(tabulate([['Alice', 24], ['Bob', 19]], headers=['Name', 'Age'], tablefmt='orgtbl'))
| Name | Age |
|--------+-------|
| Alice | 24 |
| Bob | 19 |
2. PrettyTable: https://pypi.python.org/...
Salting Your Password: Best Practices?
... Site-wide random salt is bad, since an attacker can precompute rainbow tables and grab your entire user database. If you don't understand this, please don't write login/security systems :) - you NEED per-user salts.
– snemarch
Mar 23 '09 at 20:52
...
Does the join order matter in SQL?
... neither predicate can be satisfied by a row in which all columns from one table are NULL, than to say that it's associative as long as the predicates don't involve IS NULL or 'a function that is related to nulls'. One can easily imagine a predicate that satisfies the former description but not the ...
sqlalchemy: how to join several tables by one query?
...teger primary keys for everything, but whatever):
class User(Base):
__tablename__ = 'users'
email = Column(String, primary_key=True)
name = Column(String)
class Document(Base):
__tablename__ = "documents"
name = Column(String, primary_key=True)
author_email = Column(String,...