大约有 37,000 项符合查询结果（耗时：0.0315秒） [XML]
Select distinct values from a table field
...M. What I want to do is get a list of distinct values within a field on my table .... the equivalent of one of the following:
...
MySQL load NULL values from CSV data
... up containing an empty string:
LOAD DATA INFILE '/tmp/testdata.txt'
INTO TABLE moo
FIELDS TERMINATED BY ","
LINES TERMINATED BY "\n"
(one, two, three, @vfour, five)
SET four = NULLIF(@vfour,'')
;
If they're all possibly empty, then you'd read them all into variables and have multiple SET stateme...
How to align 3 divs (left/center/right) inside another div?
...ide another div.
#container {
display: flex; /* establish flex container */
flex-direction: row; /* default value; can be omitted */
flex-wrap: nowrap; /* default value; can be omitted */
justify-content: space-between; /* switched from defau...
How do I create a unique constraint that also allows nulls?
...
This very problem hits ADO.NET DataTables too. So even that I can allow nulls in the backing field using this method, the DataTable won't let me store NULLs in a unique column in the first place. If anyone knows a solution for that, please post it here
...
When to use UICollectionView instead of UITableView?
I found that UICollectionView is like an upgraded version of UITableView introduced in iOS6, but when should I choose UICollectionView instead of UITableView ?
...
Which SQL query is faster? Filter on Join criteria or Where clause?
...LEFT JOIN.
In your very case this will look like this:
SELECT *
FROM TableA a
LEFT JOIN
TableXRef x
ON x.TableAID = a.ID
AND a.ID = 1
LEFT JOIN
TableB b
ON x.TableBID = b.ID
or this:
SELECT *
FROM TableA a
LEFT JOIN
TableXRef x
ON x.TableAI...
MySQL: Large VARCHAR vs. TEXT?
I've got a messages table in MySQL which records messages between users. Apart from the typical ids and message types (all integer types) I need to save the actual message text as either VARCHAR or TEXT. I'm setting a front-end limit of 3000 characters which means the messages would never be inserte...
PostgreSQL - fetch the row which has the Max value for a column
I'm dealing with a Postgres table (called "lives") that contains records with columns for time_stamp, usr_id, transaction_id, and lives_remaining. I need a query that will give me the most recent lives_remaining total for each usr_id
...
Make body have 100% of the browser height
...the best solution:
html {
width: 100%;
height: 100%;
display: table;
}
body {
width: 100%;
display: table-cell;
}
html, body {
margin: 0px;
padding: 0px;
}
It is dynamic in that the html and the body elements will expand automatically if their contents overflow. I t...
Difference between partition key, composite key and clustering key in Cassandra?
...neral concept to indicate one or more columns used to retrieve data from a Table.
The primary key may be SIMPLE and even declared inline:
create table stackoverflow_simple (
key text PRIMARY KEY,
data text
);
That means that it is made by a single column.
But the primary ke...