大约有 3,552 项符合查询结果（耗时：0.0167秒） [XML]
Best explanation for languages without null
...y "mathematicians" call NaN "nullity" and say it compares equal to itself. SQL treats nulls as not equal to anything (so they behave like NaNs). One wonders what happens when you try to store ±∞, ±0, and NaNs into the same database column (there are 253 NaNs, half of which are "negative").
To m...
Error renaming a column in MySQL
...
The standard Mysql rename statement is:
ALTER [ONLINE | OFFLINE] [IGNORE] TABLE tbl_name
CHANGE [COLUMN] old_col_name new_col_name column_definition
[FIRST|AFTER col_name]
for this example:
ALTER TABLE xyz CHANGE manufacurerid manufac...
Sequence contains no elements?
...stID == id
select p).Single();
Also; if this is LINQ-to-SQL, then in the current version you get a slightly better behaviour if you use the form:
var id = ID;
BlogPost post = dc.BlogPosts.Single(p => p.BlogPostID == id);
...
typecast string to integer - Postgres
...uery failed: ERROR: invalid input syntax for integer: ""
Problem
PostgreSQL has no pre-defined function for safely type casting any string into an integer.
Solution
Create a user-defined function inspired by PHP's intval() function.
CREATE FUNCTION intval(character varying) RETURNS integer AS ...
Unknown column in 'field list' error on MySQL Update query
I keep getting MySQL error #1054, when trying to perform this update query:
11 Answers
...
What is the best extension for SQLite database files? [closed]
...specific naming convention, but what extension do you recommend when using SQLite?
5 Answers
...
Manipulating an Access database from Java without ODBC
...ss databases without using ODBC. It uses two other packages, Jackcess and HSQLDB, to perform these tasks. The following is a brief overview of how to get it set up.
Option 1: Using Maven
If your project uses Maven you can simply include UCanAccess via the following coordinates:
groupId: net.s...
How to get Last record from Sqlite?
...
This is very bad request for that purpose because sqlite should sort all records by their id (slow) before returning the result, Stephen Nguyen gave optimal request with DESC and LIMIT 1
– Artem Zinnatullin
Nov 15 '13 at 8:13
...
What is a stack trace, and how can I use it to debug my application errors?
...ot insert: [com.example.myproject.MyEntity]
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:96)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
at org.hibernate.id.insert.AbstractSelectingDelegate.performInsert(AbstractSelec...
The specified type member 'Date' is not supported in LINQ to Entities. Only initializers, entity mem
...
DateTime.Date cannot be converted to SQL. Use EntityFunctions.TruncateTime method to get date part.
var eventsCustom = eventCustomRepository
.FindAllEventsCustomByUniqueStudentReference(userDevice.UniqueStudentReference)
.Where(x => EntityFunctions.TruncateT...