大约有 48,000 项符合查询结果（耗时：0.0638秒） [XML]
JPA: How to have one-to-many relation of the same Entity type
...f the relationship is the same. The general case is detailed in Section 2.10.2 of the JPA 2.0 spec.
Here's a worked example. First, the entity class A:
@Entity
public class A implements Serializable {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
@ManyToOne
...
How to find gaps in sequential numbering in mysql?
...sible) answer
Here's version that works on table of any size (not just on 100 rows):
SELECT (t1.id + 1) as gap_starts_at,
(SELECT MIN(t3.id) -1 FROM arrc_vouchers t3 WHERE t3.id > t1.id) as gap_ends_at
FROM arrc_vouchers t1
WHERE NOT EXISTS (SELECT t2.id FROM arrc_vouchers t2 WHERE t2.i...
Backbone.js fetch with parameters
...owLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by \u003ca href=\"https://imgur.com/\"\u003e\u003csvg class=\"svg-icon\...
Returning the product of a list
...as ne
# from functools import reduce # python3 compatibility
a = range(1, 101)
%timeit reduce(lambda x, y: x * y, a) # (1)
%timeit reduce(mul, a) # (2)
%timeit np.prod(a) # (3)
%timeit ne.evaluate("prod(a)") # (4)
In the following configuration:
a...
Get value from JToken that may not exist (best practices)
...ypes and the ?? operator:
width = jToken.Value<double?>("width") ?? 100;
share
|
improve this answer
|
follow
|
...
mysql - how many columns is too many?
...able structure should reflect your domain model; if you really do have 70 (100, what have you) attributes that belong to the same entity there's no reason to separate them into multiple tables.
share
|
...
Removing leading zeroes from a field in a SQL statement
...ove the leading zeroes from a particular field, which is a simple VARCHAR(10) field. So, for example, if the field contains '00001A', the SELECT statement needs to return the data as '1A'.
...
What is difference between Collection.stream().forEach() and Collection.forEach()?
...
River
7,10499 gold badges4646 silver badges5959 bronze badges
answered Apr 23 '14 at 0:14
Stuart MarksStuart ...
Automatic prune with Git fetch or pull
...
rjmunro
23.9k1818 gold badges101101 silver badges127127 bronze badges
answered Sep 10 '13 at 12:25
VonCVonC
...
Optimise PostgreSQL for fast testing
...
10
I can also recommend PostgreSQL 9.0 High Performance by @GregSmith, it's really a great read. The book covers every aspect of performance t...