sqlperformance

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SQL - how to efficiently select distinct records

I\'ve got a very performance sensitive SQL Server DB. I need to make an efficient select on the following problem:[详细]

2023-04-09 18:55 分类：问答
Does SQL Server propagate WHERE conditions in complex views?

I\'ve followed this question with a full example in case it isn\'t clear what I mean from the question.[详细]

2023-03-30 19:01 分类：问答
SELECT clause using IN ... very slow?

Could you guys please review the following query to an Oracle DB and point out what\'s wrong: SELECT t1.name FROM t1, t2 WHERE t1.id = t2.id AND t2.empno IN (1, 2, 3, …, 200)[详细]

2023-03-27 16:34 分类：问答
Get Day, Month, Year, Lifetime total records with one query w/ optimizations

I have a Postgres DB running 7.4 (Yeah we\'re in the midst of upgrading) I have four separate queries to get the Daily, Monthly, Yearly and Lifetime record counts[详细]

2023-03-08 03:53 分类：问答
Why does SQL cost explode with simple "or"?

I have the following statement to find unambiguous names in my data (~1 Million entries): select Prename, Surname from person p1[详细]

2023-03-08 00:25 分类：问答
Query performance WHERE clause contains IN (subquery)

SELECT Trade.TradeId, Trade.Type, Trade.Symbol, Trade.TradeDate, SUM(TradeLine.Notional) / 1000 AS Expr1[详细]

2023-03-05 01:15 分类：问答
Proper MySQL way to add a column from one table to another

I have a large table (~10 million records) that contains several keys into other, smaller tables.The keys are unique in each of the smaller tables but not in the large one.I woul开发者_Python百科d lik[详细]

2023-02-15 07:58 分类：问答
Optimise multiple OR query

I have a Database table where I need to validate if a user has entered in the same or partly the same information.[详细]

2023-02-05 20:21 分类：问答
SQL Server 2000 Perforamance Question - Large Table

Have a larg开发者_开发技巧e table that is fast approaching 11 million records. (20 columns in the table).[详细]

2023-01-27 16:20 分类：问答
What aspects of a sql query are relatively costly to one another? Joins? Num of records? columns selected?

How costly would SELECT One, Two, Three be com开发者_如何学Cpared to SELECT One, Two, Three, ..... N-Column[详细]

2023-01-25 08:09 分类：问答