The previous article described LINQ, and by the way, the where operation, this begins with the LINQ to SQL statement, which allows you to understand from a statement's perspective that Linq,linq includes LINQ to Objects, LINQ to DataSets, LINQ to
select/distinct operatorApplication Scenario : O (∩_∩) o ... Query for Bai.Description : Unlike the SELECT function in the SQL command, the SELECT and the clauses in the query expression are placed at the end of the expression and the variables in
Linq to SQL (Group By/Having/Count/Sum/Min/Max/Avg operator ),Group By/Having Operator
Applicable scenarios: Grouping data. narrow down the scope of data for us.
Description: Assigns and returns the enumerated objects after grouping the input
Using SQL functions, you can directly calculate the average, total, minimum, maximum, sum, standard deviation, and variance statistics of database data in a query of a SELECT statement. You can also use these SQL functions when using a Recordset
The results returned by the recent SQL query cause a ORA-06502 error to the PL/SQL variable. The error description is ORA-06502: PL/SQL: numeric or value error: character string buffer too small. obviously, the length of the character variable
30. Microsoft SQL Server ManagementAutomatic Setting of SQL ServerDatabase Maintenance PlanSummaryUsing appropriate settings and performing routine maintenance tasks in the database is the key to optimizing the server. This chapter describes the
The customer mentioned that the system was slow recently, and sampled an awr report, and found that the following SQL statement has been executed for a long time SELECTMAX (dmsample0 _. ORD) ASx0_0_FROMHF_DM_SAMPLEdmsample0_WHERE (dmsample0 _.
MS SQL Server Query optimization methodThere are many reasons for the slow speed of queries, which are common1, no indexes, or no indexes (this is the most common problem with query slowness, is the flaw in programming)2, I/o throughput is small,
18. Create and use a view tableView tableView table conceptsCreate a viewModify and delete a tableEnhanced viewing table functionality in SQL Server 2000SummaryIn Chapter 17th, we learned about indexes. indexes are a secondary database structure
Single-record functions in SQL
1. ASCIIReturns the decimal number corresponding to the specified character;
SQL> select ASCII ('A') A, ASCII ('A') A, ASCII ('0') zero, ASCII ('') space from dual;
A A zero space
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