大约有 9,000 项符合查询结果（耗时：0.0321秒） [XML]
Are there disadvantages to using a generic varchar(255) for all text-based fields?
...ld always store 255 characters.
But since you tagged this question with MySQL, I'll mention a MySQL-specific tip: as rows are copied from the storage engine layer to the SQL layer, VARCHAR fields are converted to CHAR to gain the advantage of working with fixed-width rows. So the strings in memor...
How to get the last N records in mongodb?
... order mixed up ... your sort() should be run last, not first (much like a SQL ORDER BY) .find({}).skip(1).limit(50).sort({"date":-1})
– Justin Jenkins
Mar 6 '12 at 19:11
...
How do I create a PDO parameterized query with a LIKE statement?
...
thanks. had similar issue with csharp + Mysql + ODBC using like it would not return any rows using "select * from table where column like '%?%';" but will if I do like you did "select * from table where column like ?;" and set the parameter string so: string frag = $...
Hibernate throws org.hibernate.AnnotationException: No identifier specified for entity: com..domain.
...otations on it whatsoever - leave it a simple pojo.
Update: In regards to SQL views, Hibernate docs write:
There is no difference between a view and a base table for a Hibernate mapping. This is transparent at the database level
...
MySQL vs MySQLi when using PHP [closed]
Which is better, MySQL or MySQLi? And why? Which should I use?
6 Answers
6
...
PostgreSQL “DESCRIBE TABLE”
How do you perform the equivalent of Oracle's DESCRIBE TABLE in PostgreSQL (using the psql command)?
22 Answers
...
Best way to check for “empty or null value”
What is best way to check if value is null or empty string in Postgres sql statements?
10 Answers
...
How to get the CPU Usage in C#?
...up with this. I needed it for an 8 core machine where I wanted to monitor SQL server. For the code below then I passed in "sqlservr" as appName.
private static void RunTest(string appName)
{
bool done = false;
PerformanceCounter total_cpu = new PerformanceCounter("Process", "% Processor T...
Using group by on multiple columns
... values in a given column
COUNT(*) returns the number of rows in a table
SQL script examples about using aggregate functions:
Let's say we need to find the sale orders whose total sale is greater than $950. We combine the HAVING clause and the GROUP BY clause to accomplish this:
SELECT
orderI...
Specifying column name in a “references” migration
...ore info on migrations in general, and you may even end up putting calling SQL code directly in your migration. I would say ignore it, as it isn't a normal part of rails, you will get 0 performance out of it, as rails' default generated SQL queries take no advantage of it. link
...