sql-server-2012

问题 I have an ordinary one-to-many relation: customer.id = order.customerid I want to find customers who have no associated orders. I tried: -- one record select * from customers where id = 123 -- no records select * from orders where customerid = 123 -- NO RECORDS select * from customers where id not in (select customerid from orders) -- many records, as expected. select * from customers where not exist (select customerid from orders where customers.customerid = customer.id) Am I mistaken, or

问题 What is the index creating strategy? Is it possible to create more than one non-clustered index on the same column in SQL Server? How about creating clustered and non-clustered on same column? Very sorry, but indexing is very confusing to me. Is there any way to find out the estimated query execution time in SQL Server? 回答1: The words are rather logical and you'll learn them quite quickly. :) In layman's terms, SEEK implies seeking out precise locations for records, which is what the SQL

问题 excuse the bad title but I couldn't find a good way to express what I want in abstract terms. Anyway I have 3 tables tbl_product: PID | productname 1 | product 1 2 | product 2 3 | product 3 4 | product 4 .. tbl_categories, motherCategory allows me to nest categories: CID | categoriename | motherCategory 1 | electronics | NULL 2 | clothing | NULL 3 | Arduino | 1 4 | Casings, extra's | 3 .. tbl_productInCategory PID and CID are foreign keys to PID and CID in tbl_product and tbl_categories

问题 I am working on an application that allows users to dynamically choose what they see. The list of columns and tables those belong to is huge. I'm working on building a dynamic query but I don't want to have to store all the join logic if I don't have too. An example is I have a query that has LEFT JOINS for 10 tables but I only select and filter by one table. Is SQL Server 2012 Smart enough to not join on the other tables that are not needed? I know Oracle's DBMS works like this but my

问题 I got a table with 20 columns. One of the columns contains multiple values separated by a semicolon. It looks like this: -9;-9;-1;-9;-9;-9;-9;-9;-1;-9;-9;-9;-9;-9;-9;-9;-9;-9;-1;-9;-9;-9;-9;-9;-9;-9;-9;-9;-1;-9;-1;-9;-9;-9;-1;-9;-9;-9;-9;-9;-9;-1;-1;-1;-1;-9;-1;-1;-9;-9;-9;-9;-1;-9;-1;-9;-9;-9;-1;-9;-1;-9;-1;-9;-9;-9;-9;-1;-9;-9;-1;-1;-9;-1;-1;0000;FFF8;-9;-9;-9;-1;-9;-1;-9;FFF6;-9;-1;-9;-1;-9;-1;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9;-9 It contains always 115

问题 I have a JSON source that has a weird layout where there are unknown amount of columns. https://theunitedstates.io/congress-legislators/committee-membership-current.json The format is like the following: ColumnHeaders => HLAG HSAG HSAG01 .... to unknown Single row of Data JSON JSON JSON How can I get the data like this: Col1 Col2 HLAG JSON HSAG JSON HSAG01 JSON I am currently working in SSIS so I have C# solutions available to me. I just don't know how to deal with unknown columns in SSIS.

问题 My customers have very small databases of sizes 50 t0 100 MBs. We are using SQL Server 2014. The backup operations are scheduled properly. Can I recommend them to have the maintenance jobs for Index Maintenance, Update Statistics and DBCC CheckDB? How deep it will affect if these jobs are not taken care? 回答1: too vague to answer precisely, it depends a lot on the kind of activity done on the DB, the recovery model used. In the simple recovery mode, which use just db file without transaction

问题 I've read a few variations of this question, but the solutions don't seem to be working. I wish to dynamically create a "Subgroup" for each "OrderNo" & "GroupID". Subgroups should be ordered by "OrderLine" eg: (Expected outcome) OrderNo OrderLine GroupID Subgroup ------------------------------------ 10463 1 798 1 10463 2 799 2 10463 3 797 3 10463 5 65 4 10463 6 65 4 10463 7 65 4 10481 4 917 1 10481 5 918 2 10481 6 131 3 10481 7 131 3 10481 8 131 3 10481 9 130 4 I've used Dense_Rank() to

问题 I am interested in converting a date value to CYYMMDD using native SQL Server 2012 functions. I checked here: http://www.sql-server-helper.com/tips/date-formats.aspx and couldn't find anything. Anyone know? C stands for century I guess... 回答1: Have you looked at the new FORMAT function in SQL Server 2012? http://msdn.microsoft.com/en-us/library/hh213505.aspx You should be able to use something like this: SELECT FORMAT(YourDateColumn, 'yyyyMMdd') or whatever you really want to use - basically,

问题 The suggested duplicate doesn't answer the question in the title. I want to execute two MSSQL commands without any other "user" (I'm not sure what's the correct term) executing a command between them. Searching, I have found two ways that seem like they would achieve that but am unsure about them: Use TABLOCK. - But I've seen it being considered bad practice. Use a transaction - But all I could find was that it will be atomic, and not necessarily locking out other actions. What way is the