大约有 6,200 项符合查询结果（耗时：0.0212秒） [XML]
SQL join: selecting the last records in a one-to-many relationship
Suppose I have a table of customers and a table of purchases. Each purchase belongs to one customer. I want to get a list of all customers along with their last purchase in one SELECT statement. What is the best practice? Any advice on building indexes?
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How to place div side by side
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Using CSS display property - which can be used to make divs act like a table:
<div style="width: 100%; display: table;">
<div style="display: table-row">
<div style="width: 600px; display: table-cell;"> Left </div>
<div style="display: table-ce...
What's the difference(s) between .ToList(), .AsEnumerable(), AsQueryable()?
...ual type: {0}", obj.GetType().Name);
}
Let's try an arbitrary linq-to-sql Table<T>, which implements IQueryable:
ReportTypeProperties(context.Observations);
ReportTypeProperties(context.Observations.AsEnumerable());
ReportTypeProperties(context.Observations.AsQueryable());
The result:
Compil...
How to think in data stores instead of databases?
...trained my mind to think 100% in object relationships that map directly to table structures, and now it's hard to see anything differently. I can understand some of the benefits of Google Datastore (e.g. performance and the ability to distribute data), but some good database functionality is sacrif...
Stored procedure slow when called from web, fast from Management Studio
... change:
ALTER PROCEDURE [dbo].[sproc]
@param1 int,
AS
SELECT * FROM Table WHERE ID = @param1
to:
ALTER PROCEDURE [dbo].[sproc]
@param1 int,
AS
DECLARE @param1a int
SET @param1a = @param1
SELECT * FROM Table WHERE ID = @param1a
Seems strange, but it fixed my problem.
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How to load a tsv file into a Pandas DataFrame?
...od - it was very slow and failed indexing at the end. Instead, i used read_table(), which worked much faster and without the extra param.
– Yurik
Aug 15 '14 at 9:56
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Using DISTINCT and COUNT together in a MySQL Query
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use
SELECT COUNT(DISTINCT productId) from table_name WHERE keyword='$keyword'
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Downloading MySQL dump from command line
...mp -u [uname] -p --all-databases > all_db_backup.sql
If it's specific tables within a DB, then:
$ mysqldump -u [uname] -p db_name table1 table2 > table_backup.sql
You can even go as far as auto-compressing the output using gzip (if your DB is very big):
$ mysqldump -u [uname] -p db...
SQL Server Text type vs. varchar data type [closed]
...NTEXT. You'll need to enable large value types out of row for them with sp_tableoption if you want them to be always stored out of row.
As mentioned above and here, TEXT is going to be deprecated in future releases:
The text in row option will be removed in a future version of SQL Server. Avoid usi...
How do I view the full content of a text or varchar(MAX) column in SQL Server 2008 Management Studio
... this live SQL Server 2008 (build 10.0.1600) database, there's an Events table, which contains a text column named Details . (Yes, I realize this should actually be a varchar(MAX) column, but whoever set this database up did not do it that way.)
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