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  • What are the types and inner workings of a query optimizer?

    - by Frank Developer
    As I understand it, most query optimizers are cost-based. Some can be influenced by hints like FIRST_ROWS(). Others are tailored for OLAP. Is it possible to know more detailed logic about how Informix IDS and SE's optimizers decide what's the best route for processing a query, other than SET EXPLAIN? Is there any documentation which illustrates the ranking of SELECT statements? I would imagine that "SELECT col FROM table WHERE ROWID = n" ranks 1st. What are the rest of them?.. If I'm not mistaking, Informix's ROWID is a SERIAL(INT) which allows for a max. of 2GB nrows, or maybe it uses INT9 for TB's nrows?.. However, I think Oracle uses HEX values for ROWID. Too bad ROWID can't be oftenly used, since a rows ROWID can change. So maybe ROWID is used by the optimizer as a counter? Perhaps, it could be used for implementing the query progress idea I mentioned in my "Begin viewing query results before query completes" question? For some reason, I feel it wouldn't be that difficult to report a query's progress while being processed, perhaps at the expense of some slight overhead, but it would be nice to know ahead of time: A "Google-like" estimate of how many rows meet a query's criteria, display it's progress every 100, 200, 500 or 1,000 rows, give users the ability to cancel it at anytime and start displaying the qualifying rows as they are being put into the current list, while it continues searching?.. This is just one example, perhaps we could think other neat/useful features, the ingridients are more or less there. Perhaps we could fine-tune each query with more granularity than currently available? OLTP queries tend to be mostly static and pre-defined. The "what-if's" are more OLAP, so let's try to add more control and intelligence to it? So, therefore, being able to more precisely control, not "hint-influence" a query is what's needed and therefore it would be necessary to know how the optimizers logic is programmed. We can then have Dynamic SELECT and other statements for specific situations! Maybe even tell IDS to read blocks of indexes nodes at-a-time instead of one-by-one, etc. etc.

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  • Concatenating rows from different tables into one field

    - by Markus
    Hi! In a project using a MSSQL 2005 Database we are required to log all data manipulating actions in a logging table. One field in that table is supposed to contain the row before it was changed. We have a lot of tables so I was trying to write a stored procedure that would gather up all the fields in one row of a table that was given to it, concatenate them somehow and then write a new log entry with that information. I already tried using FOR XML PATH and it worked, but the client doesn't like the XML notation, they want a csv field. Here's what I had with FOR XML PATH: DECLARE @foo varchar(max); SET @foo = (SELECT * FROM table WHERE id = 5775 FOR XML PATH('')); The values for "table", "id" and the actual id (here: 5775) would later be passed in via the call to the stored procedure. Is there any way to do this without getting XML notation and without knowing in advance which fields are going to be returned by the SELECT statement?

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  • PL/SQL - How to pull data from 3 tables based on latest created date

    - by Nancy
    Hello, I'm hoping someone can help me as I've been stuck on this problem for a few days now. Basically I'm trying to pull data from 3 tables in Oracle: 1) Orders Table 2) Vendor Table and 3) Master Data Table. Here's what the 3 tables look like: Table 1: BIZ_DOC2 (Orders table) OBJECTID (Unique key) UNIQUE_DOC_NAME (Document Name i.e. ORD-005) CREATED_AT (Date the order was created) Table 2: UDEF_VENDOR (Vendors Table): PARENT_OBJECT_ID (This matches up to the ObjectId in the Orders table) VENDOR_OBJECT_NAME (This is the name of the vendor i.e. Acme) Table 3: BIZ_UNIT (Master Data table) PARENT_OBJECT_ID (This matches up to the ObjectID in the Orders table) BIZ_UNIT_OBJECT_NAME (This is the name of the business unit i.e. widget A, widget B) Note: The Vendors Table and Master Data do not have a link between them except through the Orders table. I can join all of the data from the tables and it looks something like this: Before selecting latest order date: ORD-005 | Widget A | Acme | 3/14/10 ORD-005 | Widget B | Acme | 3/14/10 ORD-004 | Widget C | Acme | 3/10/10 Ideally I'd like to return the latest order for each vendor. However, each order may contain multiple business units (e.g. types of widgets) so if a Vendor's latest record is ORD-005 and the order contains 2 business units, here's what the result set should look like by the following columns: UNIQUE_DOC_NAME, BIZ_UNIT_OBJECT_NAME, VENDOR_OBJECT_NAME, CREATED_AT After selecting by latest order date: ORD-005 | Widget A | Acme | 3/14/10 ORD-005 | Widget B | Acme | 3/14/10 I tried using Select Max and several variations of sub-queries but I just can't seem to get it working. Any help would be hugely appreciated!

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  • Group keywords by site

    - by Skudd
    I am finding a lot of useful help here today, and I really appreciate it. This should be the last one for the day: I have a list of the top 10 keywords per site, sorted by visits, by date. The records need to be sorted as follows (excuse the formatting): 2010-05 2010-04 site1.com keyword1 apples wine keyword1 visits 100 12 keyword2 oranges water keyword2 visits 99 10 site2.com keyword1 blueberry cornbread keyword1 visits 90 100 keyword2 squares biscuits keyword2 visits 80 99 Basically what I need to accomplish involves grouping, but I can't seem to figure it out. Am I heading down the right path, or is there another way to achieve this, or is it just impossible?

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  • Converting delimited string to multiple values in mysql

    - by epo
    I have a mysql legacy table which contains an client identifier and a list of items, the latter as a comma-delimited string. E.g. "xyz001", "foo,bar,baz". This is legacy stuff and the user insists on being able to edit a comma delimited string. They now have a requirement for a report table with the above broken into separate rows, e.g. "xyz001", "foo" "xyz001", "bar" "xyz001", "baz" Breaking the string into substrings is easily doable and I have written a procedure to do this by creating a separate table, but that requires triggers to deal with deletes, updates and inserts. This query is required rarely (say once a month) but has to be absolutely up to date when it is run, so e.g. the overhead of triggers is not warranted and scheduled tasks to create the table might not be timely enough. Is there any way to write a function to return a table or a set so that I can join the identifier with the individual items on demand?

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  • How to add if statement in SQL ?

    - by shin
    I have a following MySQL with two parameters, $catname and $limit=1. And it is working fine. SELECT P.*, C.Name AS CatName FROM omc_product AS P LEFT JOIN omc_category AS C ON C.id = P.category_id WHERE C.Name = '$catname' AND p.status = 'active' ORDER BY RAND() LIMIT 0, $limit Now I want to add another parameter $order. $order can be either ODER BY RAND() or ORDER BY product_order in the table omc_product. Could anyone tell me how to write this query please? Thanks in advance.

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  • MySQL slow query

    - by andrhamm
    SELECT items.item_id, items.category_id, items.title, items.description, items.quality, items.type, items.status, items.price, items.posted, items.modified, zip_code.state_prefix, zip_code.city, books.isbn13, books.isbn10, books.authors, books.publisher FROM ( ( items LEFT JOIN bookitems ON items.item_id = bookitems.item_id ) LEFT JOIN books ON books.isbn13 = bookitems.isbn13 ) LEFT JOIN zip_code ON zip_code.zip_code = items.item_zip WHERE items.rid = $rid` I am running this query to get the list of a user's items and their location. The zip_code table has over 40k records and this might be the issue. It currently takes up to 15 seconds to return a list of about 20 items! What can I do to make this query more efficient?

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  • I'm trying to handle the updates on 2 related tables in one DetailsView using Jquery and Linq, and h

    - by Ben Reisner
    Given two related tables (reports, report_fields) where there can be many report_fields entries for each reports entry, I need to allow the user to enter new report_fields, delete existing report_fields, and re-arrange the order. Currently I am using a DetailsView to handle the editing of the reports. I added some logic to handle report_fields, and currently it allows you to succesfully re-arrange the order, but i'm a little stumped as to the best way to add new items, or delete existing items. The basic logic I have is that each report_fields is represented by a . It has a description as the text, and a field for each field in the report_fields table. I use JQuery Sortable to allow the user to re-arrange the LIs. Abbreviated Create Table Statements:(foreign key constraint ignored for brevity) create table report( id integer primary key identity, reportname varchar(250) ) create table report_fields( id integer primary key identity, reportID integer, keyname integer, keyvalue integer, field_order integer ) My abbreviated markup: <asp:DetailsView ...> ... <asp:TemplateField HeaderText="Fields"> <EditItemTemplate> <ul class="MySortable"> <asp:Repeater ID="Repeater1" runat="server" DataSource='<%# Eval("report_fields") %>'> <ItemTemplate> <li> <%# Eval("keyname") %>: <%# Eval("keyvalue") %> <input type="hidden" name="keyname[]" value='<%# Eval("keyname") %>' /> <input type="hidden" name="keyvalue[]" value='<%# Eval("keyvalue") %>' /> </li> </ItemTemplate> </asp:Repeater> </ul> </EditItemTemplate> </asp:TemplateField> </asp:DetailsView> <asp:LinqDataSource ID="LinqDataSource2" onupdating="LinqDataSource2_Updating" table=reports ... /> $(function() { $(".MySortable").sortable({ placeholder: 'MySortable-highlight' }).disableSelection(); }); Code Behind Class: public partial class Administration_AddEditReport protected void LinqDataSource2_Updating(object sender, LinqDataSourceUpdateEventArgs e) { report r = (report)e.NewObject; MyDataContext dc = new MyDataContext(); var fields = from f in dc.report_fields where f.reportID == r.id select f; dc.report_fields.DeleteAllOnSubmit(fields); NameValueCollection nvc = Request.Params; string[] keyname = nvc["keyname[]"].Split(','); string[] keyvalue = nvc["keyvalue[]"].Split(','); for (int i = 0; i < keyname.Length; i++) { report_field rf = new report_field(); rf.reportID = r.id; rf.keyname = keyname[i]; rf.keyvalue = keyvalue[i]; rf.field_order = i; dc.report_fields.InsertOnSubmit(rf); } dc.SubmitChanges(); } }

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  • PIVOT / UNPIVOT IN SQL 2008

    - by Nev_Rahd
    Hello I got child / parent tables as below. MasterTable: MasterID, Description ChildTable ChildID, MasterID, Description. Using PIVOT / UNPIVOT how can i get result as below in single row. if (MasterID : 1 got x child records) MasterID, ChildID1, Description1, ChildID2, Description2....... ChildIDx, Descriptionx Thanks

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  • Compiled Queries and "Parameters cannot be sequences"

    - by David B
    I thought that compiled queries would perform the same query translation as DataContext. Yet I'm getting a run-time error when I try to use a query with a .Contains method call. Where have I gone wrong? //private member which holds a compiled query. Func<DataAccess.DataClasses1DataContext, List<int>, List<DataAccess.TestRecord>> compiledFiftyRecordQuery = System.Data.Linq.CompiledQuery.Compile <DataAccess.DataClasses1DataContext, List<int>, List<DataAccess.TestRecord>> ((dc, ids) => dc.TestRecords.Where(tr => ids.Contains(tr.ID)).ToList()); //this method calls the compiled query. public void FiftyRecordCompiledQueryByID() { List<int> IDs = GetRandomInts(50); //System.NotSupportedException //{"Parameters cannot be sequences."} List<DataAccess.TestRecord> results = compiledFiftyRecordQuery (myContext, IDs); }

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  • Transactional isolation level needed for safely incrementing ids

    - by Knut Arne Vedaa
    I'm writing a small piece of software that is to insert records into a database used by a commercial application. The unique primary keys (ids) in the relevant table(s) are sequential, but does not seem to be set to "auto increment". Thus, I assume, I will have to find the largest id, increment it and use that value for the record I'm inserting. In pseudo-code for brevity: id = select max(id) from some_table id++ insert into some_table values(id, othervalues...) Now, if another thread started the same transaction before the first one finished its insert, you would get two identical ids and a failure when trying to insert the last one. You could check for that failure and retry, but a simpler solution might be setting an isolation level on the transaction. For this, would I need SERIALIZABLE or a lower level? Additionally, is this, generally, a sound way of solving the problem? Are the any other ways of doing it?

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  • why this left join query failed to load all the data in left table ?

    - by lzyy
    users table +-----+-----------+ | id | username | +-----+-----------+ | 1 | tom | | 2 | jelly | | 3 | foo | | 4 | bar | +-----+-----------+ groups table +----+---------+-----------------------------+ | id | user_id | title | +----+---------+-----------------------------+ | 2 | 1 | title 1 | | 4 | 1 | title 2 | +----+---------+-----------------------------+ the query SELECT users.username,users.id,count(groups.title) as group_count FROM users LEFT JOIN groups ON users.id = groups.user_id result +----------+----+-------------+ | username | id | group_count | +----------+----+-------------+ | tom | 1 | 2 | +----------+----+-------------+ where is the rest users' info? the result is the same as inner join , shouldn't left join return all left table's data? PS:I'm using mysql

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  • Conversion failed: SqlParameter and DateTime

    - by Tim
    I'm changing old,vulnerable sqlcommands with SqlParameters but get a SqlException: System.Data.SqlClient.SqlException {"Conversion failed when converting datetime from character string."} on sqlCommand.ExecuteScalar() Dim sqlString As String = _ "SELECT TOP 1 " & _ "fiSL " & _ "FROM " & _ "tabData AS D " & _ "WHERE " & _ "D.SSN_Number = '@SSN_Number' " & _ "AND D.fiProductType = 1 " & _ "AND D.Repair_Completion_Date > '@Repair_Completion_Date' " & _ "ORDER BY " & _ "D.Repair_Completion_Date ASC" Dim obj As Object Dim sqlCommand As SqlCommand Try sqlCommand = New SqlCommand(sqlString, Common.MyDB.SqlConn_RM2) sqlCommand.CommandTimeout = 120 sqlCommand.Parameters.AddWithValue("@SSN_Number", myClaim.SSNNumber) sqlCommand.Parameters.AddWithValue("@Repair_Completion_Date", myClaim.RepairCompletionDate) If Common.MyDB.SqlConn_RM2.State <> System.Data.ConnectionState.Open Then Common.MyDB.SqlConn_RM2.Open() obj = sqlCommand.ExecuteScalar() Catch ex As Exception Dim debug As String = ex.ToString Finally Common.MyDB.SqlConn_RM2.Close() End Try myClaim.RepairCompletionDate is a SQLDateTime. Do i have to remove the quotes in the sqlString to compare Date columns? But then i dont get a exception but incorrect results.

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  • When is referential integrity not appropriate?

    - by Curtis Inderwiesche
    I understand the need to have referential integrity for limiting specific values on entry or possibly preventing them from removal upon a request of deletion. However, I am unclear as to a valid use case which would exclude this mechanism from always being used. I guess this would fall into several sub-questions: When is referential integrity not appropriate? Is it appropriate to have fields containing multiple and/or possibly incomplete subsets of a foreign key's list? Typically, should this be a schema structure design decision or an interface design decision? (Or possibly neither or both) Thoughts?

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  • Violation of PRIMARY KEY constraint 'PK_

    - by abhi
    hi am trying to write a code in which i need to perform a update but on primary keys how do i achieve it i have written the following code: kindly look at it let me know where m wrong Protected Sub rgKMSLoc_UpdateCommand(ByVal source As Object, ByVal e As Telerik.Web.UI.GridCommandEventArgs) Handles rgKMSLoc.UpdateCommand Try KAYAReqConn.Open() If TypeOf e.Item Is GridEditableItem Then Dim strItemID As String = CType(e.Item.FindControl("hdnID"), HiddenField).Value Dim strrcmbLocation As String = CType(e.Item.FindControl("rcmbLocation"), RadComboBox).SelectedValue Dim strKubeLocation As String = CType(e.Item.FindControl("txtKubeLocation"), TextBox).Text Dim strCSVCode As String = CType(e.Item.FindControl("txtCSVCode"), TextBox).Text SQLCmd = New SqlCommand("SELECT * FROM MstKMSLocKubeLocMapping WHERE LocationID= '" & rcmbLocation.SelectedValue & "'", KAYAReqConn) Dim dr As SqlDataReader dr = SQLCmd.ExecuteReader If dr.HasRows Then lblMsgWarning.Text = "<font color=red>""User ID Already Exists" Exit Sub End If dr.Close() SQLCmd = New SqlCommand("UPDATE MstKMSLocKubeLocMapping SET LocationID=@Location,KubeLocation=@KubeLocation,CSVCode=@CSVCode WHERE LocationID = '" & strItemID & "'", KAYAReqConn) SQLCmd.Parameters.AddWithValue("@Location", Replace(strrcmbLocation, "'", "''")) SQLCmd.Parameters.AddWithValue("@KubeLocation", Replace(strKubeLocation, "'", "''")) SQLCmd.Parameters.AddWithValue("@CSVCode", Replace(strCSVCode, "'", "''")) SQLCmd.Parameters.AddWithValue("@Status", "A") SQLCmd.ExecuteNonQuery() lblMessageUpdate.Text = "<font color=blue>""Record Updated SuccessFully" SQLCmd.Dispose() rgKMSLoc.Rebind() End If Catch ex As Exception Response.Write(ex.ToString) Finally KAYAReqConn.Close() End Try End Sub this is my designer page' Location: ' / ' DataSourceID="dsrcmbLocation" DataTextField="Location" DataValueField="LocationID" Height="150px" Kube Location: ' Class="forTextBox" MaxLength="4" onkeypress="return filterInput(2,event);" CSV Code: ' Class="forTextBox" MaxLength="4" onkeypress="return filterInput(2,event);" <tr class="tableRow"> <td colspan="2" align="center" class="tableCell"> <asp:ImageButton ID="btnUpdate" runat="server" CommandName="Update" CausesValidation="true" ValidationGroup="Update" ImageUrl="~/Images/update.gif"></asp:ImageButton> <asp:ImageButton ID="btnCancel" runat="server" CausesValidation="false" CommandName="Cancel" ImageUrl="~/Images/No.gif"></asp:ImageButton> </td> </tr> </table> </FormTemplate> </EditFormSettings> Locationid is my primary key

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  • How Can I truncate Multiple Tables in MySql?

    - by Luiscencio
    I need to clear all my inventory tables. I've tryed SELECT 'TRUNCATE TABLE ' + TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME LIKE 'inventory%' but I get this error: Truncated incorrect DOUBLE value: 'TRUNCATE TABLE ' Error Code 1292 if this is the correct way, then what am I doing wrong?

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  • PostgreSQL: SELECT all fields, filter some

    - by Adam Matan
    Hi, In one of our databases, there is a table with dozens of columns, one of which is a geometry column. I want to SELECT rows from the table, with the geometry transformed to another SRID. I want to use something like: `SELECT *` in order to avoid: SELECT col_a, col_b, col_c, col_d, col_e, col_f, col_g, col_h, transform(the_geom, NEW_SRID), ..., col_z Any ideas? Adam

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  • Error invoking stored procedure with input parameter from ADO.Net

    - by George2
    Hello everyone, I am using VSTS 2008 + C# + .Net 3.5 + ADO.Net. Here is my code and related error message. The error message says, @Param1 is not supplied, but actually it is supplied in my code. Any ideas what is wrong? System.Data.SqlClient.SqlException: Procedure or function 'Pr_Foo' expects parameter '@Param1', which was not supplied. class Program { private static SqlCommand _command; private static SqlConnection connection; private static readonly string _storedProcedureName = "Pr_Foo"; private static readonly string connectionString = "server=.;integrated Security=sspi;initial catalog=FooDB"; public static void Prepare() { connection = new SqlConnection(connectionString); connection.Open(); _command = connection.CreateCommand(); _command.CommandText = _storedProcedureName; _command.CommandType = CommandType.StoredProcedure; } public static void Dispose() { connection.Close(); } public static void Run() { try { SqlParameter Param1 = _command.Parameters.Add("@Param1", SqlDbType.Int, 300101); Param1.Direction = ParameterDirection.Input; SqlParameter Param2 = _command.Parameters.Add("@Param2", SqlDbType.Int, 100); portal_SiteInfoID.Direction = ParameterDirection.Input; SqlParameter Param3 = _command.Parameters.Add("@Param3", SqlDbType.Int, 200); portal_RoleInfoID.Direction = ParameterDirection.Input; _command.ExecuteScalar(); } catch (Exception e) { Console.WriteLine(e); } } static void Main(string[] args) { try { Prepare(); Thread t1 = new Thread(Program.Run); t1.Start(); t1.Join(); Dispose(); } catch (Exception ex) { Console.WriteLine(ex.Message + "\t" + ex.StackTrace); } } } Thanks in advance, George

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  • Should I include user_id in multiple tables?

    - by Drarok
    I'm at the planning stages of a multi-user application where each user will only have access their own data. There'll be a few tables that relate to each other, so I could use JOINs to ensure they're accessing only their data, but should I include user_id in each table? Would this be faster? It would certainly make some of the queries easier in the long run. Thanks!

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  • What resources will help me understand the fundamentals of Relational Database Systems.

    - by Rachel
    This are few of the fundamental database questions which has always given me trouble. I have tried using google and wiki but I somehow I miss out on understanding the functionality rather than terminology. If possible would really appreciate if someone can share more insights on this questions using some visual representative examples. What is a key? A candidate key? A primary key? An alternate key? A foreign key? What is an index and how does it help your database? What are the data types available and when to use which ones?

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  • Can't return a List from a Compiled Query.

    - by Andrew
    I was speeding up my app by using compiled queries for queries which were getting hit over and over. I tried to implement it like this: Function Select(ByVal fk_id As Integer) As List(SomeEntity) Using db As New DataContext() db.ObjectTrackingEnabled = False Return CompiledSelect(db, fk_id) End Using End Function Shared CompiledSelect As Func(Of DataContext, Integer, List(Of SomeEntity)) = _ CompiledQuery.Compile(Function(db As DataContext, fk_id As Integer) _ (From u In db.SomeEntities _ Where u.SomeLinkedEntity.ID = fk_id _ Select u).ToList()) This did not work and I got this error message: Type : System.ArgumentNullException, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 Message : Value cannot be null. Parameter name: value However, when I changed my compiled query to return IQueryable instead of List like so: Function Select(ByVal fk_id As Integer) As List(SomeEntity) Using db As New DataContext() db.ObjectTrackingEnabled = False Return CompiledSelect(db, fk_id).ToList() End Using End Function Shared CompiledSelect As Func(Of DataContext, Integer, IQueryable(Of SomeEntity)) = _ CompiledQuery.Compile(Function(db As DataContext, fk_id As Integer) _ From u In db.SomeEntities _ Where u.SomeLinkedEntity.ID = fk_id _ Select u) It worked fine. Can anyone shed any light as to why this is? BTW, compiled queries rock! They sped up my app by a factor of 2.

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  • mysql query for getting all messages that belong to user's contacts

    - by aharon
    So I have a database that is setup sort of like this (simplified, and in terms of the tables, all are InnoDBs): Users: contains based user authentication information (uid, username, encrypted password, et cetera) Contacts: contains two rows per relationship that exists between users as (uid1, uid2), (uid2, uid1) to allow for a good 1:1 relationship (must be mutual) between users Messages: has messages that consist of a blob, owner-id, message-id (auto_increment) So my question is, what's the best MySQL query to get all messages that belong to all the contacts of a specific user? Is there an efficient way to do this?

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