大约有 13,000 项符合查询结果（耗时：0.0195秒） [XML]
Return all enumerables with yield return at once; without looping through
...ods each returning an IEnumerable<ErrorInfo>, you can use Enumerable.Concat to make your code simpler:
private static IEnumerable<ErrorInfo> GetErrors(Card card)
{
return GetMoreErrors(card).Concat(GetOtherErrors())
.Concat(GetValidationErrors())
...
PostgreSQL: Difference between text and varchar (character varying)
... article does detailed testing to show that the performance of inserts and selects for all 4 data types are similar. It also takes a detailed look at alternate ways on constraining the length when needed. Function based constraints or domains provide the advantage of instant increase of the length c...
How to concatenate two IEnumerable into a new IEnumerable?
...he same T ). I want a new instance of IEnumerable<T> which is the concatenation of both.
4 Answers
...
Best way to check for “empty or null value”
... '
Demo
Empty string equals any string of spaces when cast to char(n):
SELECT ''::char(5) = ''::char(5) AS eq1
, ''::char(5) = ' '::char(5) AS eq2
, ''::char(5) = ' '::char(5) AS eq3;
Result:
eq1 | eq2 | eq3
----+-----+----
t | t | t
Test for "null or empty string" w...
Large, persistent DataFrame in pandas
...o read the file in smaller pieces (use iterator=True, chunksize=1000) then concatenate then with pd.concat. The problem comes in when you pull the entire text file into memory in one big slurp.
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Get all table names of a particular database by SQL query?
...different sql dbms deal with schemas.
Try the following
For SQL Server:
SELECT TABLE_NAME
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_TYPE = 'BASE TABLE' AND TABLE_CATALOG='dbName'
For MySQL:
SELECT TABLE_NAME
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_TYPE = 'BASE TABLE' AND TABLE_SCHEMA='dbN...
How to convert a color integer to a hex String in Android?
...
private static String To00Hex(int value) {
String hex = "00".concat(Integer.toHexString(value));
return hex.substring(hex.length()-2, hex.length());
}
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String vs. StringBuilder
...ance difference is significant. See the KB article "How to improve string concatenation performance in Visual C#".
I have always tried to code for clarity first, and then optimize for performance later. That's much easier than doing it the other way around! However, having seen the enormous perfo...
VC DDE（Dynamic Data Exchange）与EXCEL连接 - C/C++ - 清泛网 - 专注C/C++及内核技术
...char szItem5[] = "R3C1"; char szData5[16] = "0";
//char szCmd2[] = "[SELECT(\"R3C1\")][FONT.PROPERTIES(,\"Bold\")][SAVE()][QUIT()]";
char szCmd2[] = "[SELECT(\"R3C1\")][FONT.PROPERTIES(,\"Bold\")]";
char szCmd3[] = "[SELECT(\"R3C1\")][FONT.PROPERTIES(,\"Bold\")]";
int i,j,k;
char...
Generate class from database table
...eName'
declare @Result varchar(max) = 'public class ' + @TableName + '
{'
select @Result = @Result + '
public ' + ColumnType + NullableSign + ' ' + ColumnName + ' { get; set; }
'
from
(
select
replace(col.name, ' ', '_') ColumnName,
column_id ColumnId,
case typ.name...