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  • difference between where and nested queries

    - by Chris H
    I'm not able to figure out the difference between these queries. I'm pretty sure that the first one is an equi-join. I'm not sure how the second one ISN'T the same as the first. The sub query in #2 selects all Ids from S, and then it returns all R's that also have those ID's, no? SELECT R.cname FROM R, S, WHERE R.Id = S.Id SELECT R.cname FROM R WHERE R.Id IN (SELECT S.Id FROM S)

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  • Is this a bad indexing strategy for a table?

    - by llamaoo7
    The table in question is part of a database that a vendor's software uses on our network. The table contains metadata about files. The schema of the table is as follows Metadata ResultID (PK, int, not null) MappedFieldname (char(50), not null) Fieldname (PK, char(50), not null) Fieldvalue (text, null) There is a clustered index on ResultID and Fieldname. This table typically contains millions of rows (in one case, it contains 500 million). The table is populated by 24 workers running 4 threads each when data is being "processed". This results in many non-sequential inserts. Later after processing, more data is inserted into this table by some of our in-house software. The fragmentation for a given table is at least 50%. In the case of the largest table, it is at 90%. We do not have a DBA. I am aware we desperately need a DB maintenance strategy. As far as my background, I'm a college student working part time at this company. My question is this, is a clustered index the best way to go about this? Should another index be considered? Are there any good references for this type and similar ad-hoc DBA tasks?

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  • sDesigning a database with flexible user profile

    - by Mughrabi
    I am working on a design where I can have flexible attributes for users and I am confused how to continue the design of the schema. I made a table where I kept system needed information: Table name: users id username password Now, I wish to create a profile table and have one to one relation where all the other attributes in profile table such as email, first name, last name, etc. My question is: is there a way to add a third table in which profiles will be flexible? In other words, if my clients need to create a new attribute he/she won't need any customization to the code.

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  • Most efficient way to Update with Linq2Sql

    - by pranay
    can I update my employee record as given in below function or i have to make query of employee collection first and than i update data public int updateEmployee(App3_EMPLOYEE employee) { DBContextDataContext db = new DBContextDataContext(); db.App3_EMPLOYEEs.Attach(employee); db.SubmitChanges(); return employee.PKEY; } or i have to do this public int updateEmployee(App3_EMPLOYEE employee) { DBContextDataContext db = new DBContextDataContext(); App3_EMPLOYEE emp = db.App3_EMPLOYEEs.Single(e => e.PKEY == employee.PKEY); db.App3_EMPLOYEEs.Attach(employee,emp); db.SubmitChanges(); return employee.PKEY; } But i dont want to use second option is there any efficient way to update data

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  • android : SQL Exception while querying

    - by Ram
    Team, Can you please help me to understand why I m getting the following exception. 05-07 10:57:20.652: ERROR/AndroidRuntime(470): android.database.sqlite.SQLiteException: near "1": syntax error: , while compiling: SELECT Id,Name FROM act WHERE Id 1-IJUS-1 Thanks in advance,

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  • Forcing the use of an index can improve performance?

    - by aF.
    Imagine that we have a query like this: select a.col1, b.col2 from t1 a inner join t2 b on a.col1 = b.col2 where a.col1 = 'abc' Both col1 and col2 don't have any index. If I add another restriction on the where clause, one that is always correct but with a column with an index: select a.col1, b.col2 from t1 a inner join t2 b on a.col1 = b.col2 where a.col1 = 'abc' and a.id >= 0 -- column always true and with index May the query perform faster since it may use the index on id column?

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  • entering data in sql database through asp

    - by sushant
    pass=session("password") Set objIns=server.CreateObject("adodb.connection") objIns.Open session("Psrconnect") inspass="Insert into passwords(pass) values ('&pass&')" objIns.Execute(inspass) i dont know what should be the syntax to pass the value stored in the variable. with this syntax, the value entered in the database is &pass&. can anyone plz help me out?

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  • Best way to get distinct values from large table

    - by derivation
    I have a db table with about 10 or so columns, two of which are month and year. The table has about 250k rows now, and we expect it to grow by about 100-150k records a month. A lot of queries involve the month and year column (ex, all records from march 2010), and so we frequently need to get the available month and year combinations (ie do we have records for april 2010?). A coworker thinks that we should have a separate table from our main one that only contains the months and years we have data for. We only add records to our main table once a month, so it would just be a small update on the end of our scripts to add the new entry to this second table. This second table would be queried whenever we need to find the available month/year entries on the first table. This solution feels kludgy to me and a violation of DRY. What do you think is the correct way of solving this problem? Is there a better way than having two tables?

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  • Entity diagram with tables that have foreign keys that point to a non-PK column do not show relation

    - by Jason Coyne
    I have two tables parent and child. If I make a foreign key on child that points to the primary key of parent, and then make an entity diagram, the relationship is shown correctly. If I make the foreign key point to a different column, the relationship is not shown. I have tried adding indexes to the column, but it does not have an effect. The database is sqlite, but I am not sure if that has an effect since its all hidden behind ADO.net. How do I get the relationship to work correctly?

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  • left join without duplicate values using MIN()

    - by Clipper87
    I have a table_1: id custno 1 1 2 2 3 3 and a table_2: id custno qty descr 1 1 10 a 2 1 7 b 3 2 4 c 4 3 7 d 5 1 5 e 6 1 5 f When I run this query to show the minimum order quantities from every customer: SELECT DISTINCT table_1.custno,table_2.qty,table_2.descr FROM table_1 LEFT OUTER JOIN table_2 ON table_1.custno = table_2.custno AND qty = (SELECT MIN(qty) FROM table_2 WHERE table_2.custno = table_1.custno ) Then I get this result: custno qty descr 1 5 e 1 5 f 2 4 c 3 7 d Customer 1 appears twice each time with the same minimum qty (& a different description) but I only want to see customer 1 appear once. I don't care if that is the record with 'e' as a description or 'f' as a description. How could I do this ? Thx!

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  • How do I exclude outliers from an aggregate query?

    - by Margaret
    I'm creating a report comparing total time and volume across units. Here a simplification of the query I'm using at the moment: SELECT m.Unit, COUNT(*) AS Count, SUM(m.TimeInMinutes) AS TotalTime FROM main_table m WHERE m.unit <> '' AND m.TimeInMinutes > 0 GROUP BY m.Unit HAVING COUNT(*) > 15 However, I have been told that I need to exclude cases where the row's time is in the highest or lowest 5% to try and get rid of a few wacky outliers. (As in, remove the rows before the aggregates are applied.) How do I do that?

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  • Creating a multi-row "table" as part of a SELECT

    - by Chad Birch
    I'm not really sure how to describe my question (thus the awful title), but it's related to this recent question. The problem would be easily solved if there was some way for me to create a "table" with 4 rows as part of my SELECT (to use with NOT IN or MINUS). What I mean is, I can do this: SELECT 1, 2, 3, 4; And will receive one row from the database: | 1 | 2 | 3 | 4 | But is there any way to receive the following (without using UNION, I don't really want a query that's potentially thousands of lines long with a long list)? | 1 | | 2 | | 3 | | 4 |

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  • dbo in SqlServer

    - by ala
    I'm converting database from Teradata to SqlServer. I've noticed all tables and procedures are named by the prefix "dbo." (e.g. "dbo.Table1"). I would like to know if and how I can get rid of "dbo" because it would make the conversion task a lot more easier.

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  • Problems with mysql syntax

    - by user368453
    Hello everyone !! I´m trying to create a trigger on MySQL but I´m having a sintaxe problem, which I was not able to find. If someone more experient could help me it would be great (it´s the first time I use MySQL!)... The reason why I´m creating this trigger is for deleting all the orphan "labels", which has a many-to-many relation with "service_descriptor" (this two entities are linked by service_labels). The code I have is: CREATE TRIGGER trg_delete_orphan_label AFTER DELETE FOR EACH ROW ON restdb.service_labels DELETE FROM restdb.labels WHERE EXISTS (SELECT * FROM old D LEFT_JOIN restdb.service_labels SL ON SL.id_label = D.id_label AND D.id_service = SL.id_service WHERE SL.id_label IS NULL restdb.labels.id = D.SL.id_label ); Thanks in advance !

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  • oracle query returns 4 duplicates of each row

    - by ajoe
    hello, I am Running a oracle query, it seems to work except that it returns 4 dupes of each result. here is the code: Select * from (Select a.*, rownum rnum From (SELECT NEW_USER.*, NEW_EHS_QUIZ_COMPLETE.datetime FROM NEW_USER, NEW_EHS_QUIZ_COMPLETE WHERE EXISTS(select * from NEW_EHS_QUIZ_COMPLETE where NEW_USER.id=NEW_EHS_QUIZ_COMPLETE.USER_ID) ORDER by last_name ASC ) a where rownum <= #pgtop# ) where rnum >= #pgbot# does anyone know why this isnt working properly? thanks in advance.

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  • Help with sql query

    - by user225269
    I have two tables: subject and student. I'm trying to count the number of subjects enrolled by each student. How do I do that?I'm trying the code below but it doesn't give the answer I need. Please help. SELECT COUNT( subject.SUBJECT ) , student.IDNO, student.FIRSTNAME, subject.SUBJECT FROM student, subject GROUP BY subject.SUBJECT LIMIT 0 , 30

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  • MySQL: group by and IF statement

    - by notset
    By default, parent_id = 0. I want to select all records with parent_id = 0 and only the last ones with parent_id 0. I tried this, but it didn't work: SELECT * FROM `articles` IF `parent_id` > 0 THEN GROUP BY `parent_id` HAVING COUNT(`parent_id`) >= 1 END; ORDER BY `time` DESC What could be the solution?

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  • How can I select the required records?

    - by simple
    Tables: Product: [id, name, brand_id, is_published] Brand: [id, name, is_published] Awards: [id, name] ProductAwards [product_id, award_id] How do I select the list of PUBLISHED brands along with the number of AWARDS of brand's products that are Published. I am cool with all the part except issuing the "is_published" restriction when counting Awards. I hope this is clear; can anyone just suggest where to dig?

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  • Query to bring count from comma seperated Value

    - by Mugil
    I have Two Tables One for Storing Products and Other for Storing Orders List. CREATE TABLE ProductsList(ProductId INT NOT NULL PRIMARY KEY, ProductName VARCHAR(50)) INSERT INTO ProductsList(ProductId, ProductName) VALUES(1,'Product A'), (2,'Product B'), (3,'Product C'), (4,'Product D'), (5,'Product E'), (6,'Product F'), (7,'Product G'), (8,'Product H'), (9,'Product I'), (10,'Product J'); CREATE TABLE OrderList(OrderId INT NOT NULL PRIMARY KEY AUTO_INCREMENT, EmailId VARCHAR(50), CSVProductIds VARCHAR(50)) SELECT * FROM OrderList INSERT INTO OrderList(EmailId, CSVProductIds) VALUES('[email protected]', '2,4,1,5,7'), ('[email protected]', '5,7,4'), ('[email protected]', '2'), ('[email protected]', '8,9'), ('[email protected]', '4,5,9'), ('[email protected]', '1,2,3'), ('[email protected]', '9,10'), ('[email protected]', '1,5'); Output ItemName NoOfOrders Product A 4 Product B 3 Product C 1 Product D 3 Product E 4 Product F 0 Product G 2 Product H 1 Product I 2 Product J 1 The Order List Stores the ItemsId as Comma separated value for every customer who places order.Like this i am having more than 40k Records in my dB table Now I am assigned with a task of creating report in which I should display Items and No of People ordered Items as Shown Below I Used Query as below in my PHP to bring the Orders One By One and storing in array. SELECT COUNT(PL.EmailId) FROM OrderList PL WHERE CSVProductIds LIKE '2' OR CSVProductIds LIKE '%,2,%' OR CSVProductIds LIKE '%,2' OR CSVProductIds LIKE '2,%'; 1.Is it possible to get the same out put by using Single Query 2.Does using a like in mysql query slows down the dB when the table has more no of records i.e 40k rows

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  • simple query Delete records in a table based on count logic

    - by user1905941
    a table with a pk and status column which is having values as 'Y','N','NULL' Query: get the count of records with status column as 'Y', if this count exceeds 1% of total count of records then dont delete , else delete the records in the table. i tried like this Declare v_count Number; v_count1 Number; BEGIN v_count := select count(*) from temp; v_count1 := select count(*) from temp where status = 'Y' ; v_count := v_count + ((0.1) * (v_count)) if (v_count1 > v_count) { insert into temp1 values(pk,status) } else { Delete from temp ; } END;

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