大约有 9,000 项符合查询结果（耗时：0.0202秒） [XML]
What's the difference between JPA and Hibernate? [closed]
...P (Java Community Process)
Hibernate (in 2003) provided a way to abstract SQL and allow developers to think more in terms of persisting objects (ORM). You notify hibernate about your Entity objects and it automatically generates the strategy to persist them. Hibernate provided an implementation to ...
mysql :: insert into table, data from another table?
I was wondering if there is a way to do this purely in sql:
5 Answers
5
...
Does Dispose still get called when exception is thrown inside of a using statement?
...an exception inside IDisposable.Dispose
What is the proper way to ensure a SQL connection is closed when an exception is thrown?
C# "Using" Syntax
C# USING keyword - when and when not to use it?
'using' statement vs 'try finally'
What is the C# Using block and why should I use it?
Disposable Using P...
PostgreSQL: Difference between text and varchar (character varying)
...atabase they could use constraints. See blog.jonanin.com/2013/11/20/postgresql-char-varchar which includes "an example of using TEXT and constraints to create fields with more flexibility than VARCHAR".
– Ethan
Dec 14 '15 at 13:03
...
SQLite UPSERT / UPDATE OR INSERT
I need to perform UPSERT / INSERT OR UPDATE against a SQLite Database.
7 Answers
7
...
Determine Whether Two Date Ranges Overlap
...t these operations in Snodgrass's Developing Time-Oriented Applications in SQL (PDF available online at URL), and in Date, Darwen and Lorentzos Temporal Data and the Relational Model (2002) or Time and Relational Theory: Temporal Databases in the Relational Model and SQL (2014; effectively the seco...
Spark java.lang.OutOfMemoryError: Java heap space
...Hi @samthebest how did you specify 8000 partitions? Since I am using Spark sql I can only specify partition using spark.sql.shuffle.partitions, default value is 200 should I set it to more I tried to set it to 1000 but not helping getting OOM are you aware what should be the optimal partition value ...
Database Design for Revisions?
... should contain all columns present in the first, Records table. E.g. in mysql you can easily create table with the same structure as another table (create table X like Y). And, when you are about to change structure of the Records table in your live database, you have to use alter table commands an...
Can I add a UNIQUE constraint to a PostgreSQL table, after it's already created?
...
psql's inline help:
\h ALTER TABLE
Also documented in the postgres docs (an excellent resource, plus easy to read, too).
ALTER TABLE tablename ADD CONSTRAINT constraintname UNIQUE (columns);
...
When to use CouchDB over MongoDB and vice versa
I am stuck between these two NoSQL databases.
7 Answers
7
...