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Oracle的列操作(增加列,修改列,删除列)，包括操作多列 - 数据库(内核) - 清...
...(增加列,修改列,删除列)，包括操作多列增加一列： alter table emp4 add test varchar2(10);修改一列： alter table emp4 modify test varchar2(20);删除一列：alter 增加一列：
alter table emp4 add test varchar2(10);
修改一列：
alter table emp4 modify test va...
When to use static vs instantiated classes
...y the code is much more extensible and, the most important part for me, testable. Why is it more important to be testable? Because I don't always write library code, so extensibility is not that important, but testability is important when I do refactoring. Anyways, testable code usually yields exte...
Combining “LIKE” and “IN” for SQL Server [duplicate]
...y, the IN statement creates a series of OR statements... so
SELECT * FROM table WHERE column IN (1, 2, 3)
Is effectively
SELECT * FROM table WHERE column = 1 OR column = 2 OR column = 3
And sadly, that is the route you'll have to take with your LIKE statements
SELECT * FROM table
WHERE column...
How to deselect a selected UITableView cell?
...
use this code
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
//Change the selected background view of the cell.
[tableView deselectRowAtIndexPath:indexPath animated:YES];
}
Swift 3.0:
o...
Comparison of full text search engine - Lucene, Sphinx, Postgresql, MySQL?
...egarding the indexing speed, Solr can also handle JOINS from your database tables. A higher and complex JOIN do affect the indexing speed. However, an enormous RAM config can easily tackle this situation.
The higher the RAM, The faster the indexing speed of Solr is.
ease of use and ease of i...
T-SQL get SELECTed value of stored procedure
...set
ALSO, watch out if you use the pattern: SELECT @Variable=column FROM table ...
if there are multiple rows returned from the query, your @Variable will only contain the value from the last row returned by the query.
RETURN VALUE
since your query returns an int field, at least based on how you...
When to use Hadoop, HBase, Hive and Pig?
.... It's a distributed, scalable, big data store, modelled after Google's BigTable. It stores data as key/value pairs.
Coming to Hive. It provides us data warehousing facilities on top of an existing Hadoop cluster. Along with that it provides an SQL like interface which makes your work easier, in ca...
Why is a “GRANT USAGE” created the first time I grant a user privileges?
...e MySQL server, hence USAGE. It corresponds to a row in the `mysql`.`user` table with no privileges set.
The IDENTIFIED BY clause indicates that a password is set for that user. How do we know a user is who they say they are? They identify themselves by sending the correct password for their accoun...
Build tree array from flat array in javascript
... below )
Here it is:
const createDataTree = dataset => {
let hashTable = Object.create(null)
dataset.forEach( aData => hashTable[aData.ID] = { ...aData, childNodes : [] } )
let dataTree = []
dataset.forEach( aData => {
if( aData.parentID ) hashTable[aData.parentID]....
Two single-column indexes vs one two-column index in MySQL?
...a single composite index can speed up several kinds of queries on the same table." - Multiple-Column Indexes
– AlikElzin-kilaka
Sep 9 '18 at 4:46
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