大约有 47,900 项符合查询结果（耗时：0.0612秒） [XML]
MySQL - SELECT WHERE field IN (subquery) - Extremely slow why?
...qui-join.
Make sure to group by on the primary key.
If you are on InnoDB and you only select indexed fields (and things are not too complex) than MySQL will resolve your query using only the indexes, speeding things way up.
General solution for 90% of your IN (select queries
Use this code
SEL...
How do I get SUM function in MySQL to return '0' if no values are found?
...nformation:
Given three tables (one with all numbers, one with all nulls, and one with a mixture):
SQL Fiddle
MySQL 5.5.32 Schema Setup:
CREATE TABLE foo
(
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
val INT
);
INSERT INTO foo (val) VALUES
(null),(1),(null),(2),(null),(3),(null),(4),(n...
Get pandas.read_csv to read empty values as empty string instead of nan
I'm using the pandas library to read in some CSV data. In my data, certain columns contain strings. The string "nan" is a possible value, as is an empty string. I managed to get pandas to read "nan" as a string, but I can't figure out how to get it not to read an empty value as NaN. Here's sam...
How do I get the title of the current active window using c#?
...l source code here:
http://www.csharphelp.com/2006/08/get-current-window-handle-and-caption-with-windows-api-in-c/
[DllImport("user32.dll")]
static extern IntPtr GetForegroundWindow();
[DllImport("user32.dll")]
static extern int GetWindowText(IntPtr hWnd, StringBuilder text, int count);
private ...
JSON Stringify changes time of date because of UTC
...
Recently I have run into the same issue. And it was resolved using the following code:
x = new Date();
let hoursDiff = x.getHours() - x.getTimezoneOffset() / 60;
let minutesDiff = (x.getHours() - x.getTimezoneOffset()) % 60;
x.setHours(hoursDiff);
x.setMinutes(minu...
What does it mean to start a PHP function with an ampersand?
...
An ampersand before a function name means the function will return a reference to a variable instead of the value.
Returning by reference is useful when
you want to use a function to find to
which variable a reference should b...
How to convert int to char with leading zeros?
...
I will concur on the SQL2012, but for those SQL 2008r2 and older, my solution will get the result
– GoldBishop
Feb 21 '14 at 21:33
1
...
Can you use an alias in the WHERE clause in mysql?
...e performance implications since HAVING executes after the data is fetched and WHERE executes before.
– StockB
Feb 15 '17 at 19:16
...
Can I add a UNIQUE constraint to a PostgreSQL table, after it's already created?
...
I needed an answer to this very question and started googling for the docs. Instead of the Postgres documentation, I ran into this topic at StackOverflow. So although it's a good think to reference the official docs, it's also very good to give the answer for future...
How to check if element is visible after scrolling?
...you to call a utility function that accepts the element you're looking for and if you want the element to be fully in view or partially.
function Utils() {
}
Utils.prototype = {
constructor: Utils,
isElementInView: function (element, fullyInView) {
var pageTop = $(window).scrollTo...