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  • How do I select a random record efficiently in MySQL?

    - by user198729
    mysql> EXPLAIN SELECT * FROM urls ORDER BY RAND() LIMIT 1; +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ | 1 | SIMPLE | urls | ALL | NULL | NULL | NULL | NULL | 62228 | Using temporary; Using filesort | +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ The above doesn't qualify as efficient,how should I do it properly?

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  • multi-row update table with "different" data

    - by kralco626
    I think the best way to explain this is to tell you what I have. I have two tables A and B both have columns Field1 and Field2. However Field 2 is not populated in table B I want to populate field 2 of table B with field 2 of table A where field 1 of table A matches field 1 of table B. something like update tableB set Field2 = tableA.field2 where tablea.field1 = tableb.field1. The reason this may seem so odd and obscure is that I'm tyring to do an inital data load form an old database to a new one. please let me know if you need clarification

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  • Do I need to drop index on temp table?

    - by Phil
    Hi, Fairly simple question, but I don't see it anywhere else on SO: Do indexes (indices?) on a temporary table get automatically deleted with the temporary table? I'd imagine they do but I don't really know how to check to make sure. Thanks, Phil

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  • Query to add a column depending of outcome of there columns

    - by Tam
    I have a user table 'users' that has fields like: id first_name last_name ... and have another table that determines relationships: user_id friend_id user_accepted friend_accepted .... I would like to generate a query that selects all the users but also add another field/column say 'network_status' that depends on the values of user_accepted and fiend_accepted. For example, if user_accepted is true friend_accepted is false I want the 'network_status' field to say 'request sent'. Can I possibly do this in one query? (I would prefer not to user if/else inside the query but if that's the only way so be it)

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  • Databinding in combo box

    - by muralekarthick
    Hi I have two forms, and a class, queries return in Stored procedure. Stored Procedure: ALTER PROCEDURE [dbo].[Payment_Join] @reference nvarchar(20) AS BEGIN -- SET NOCOUNT ON added to prevent extra result sets from -- interfering with SELECT statements. SET NOCOUNT ON; -- Insert statements for procedure here SELECT p.iPaymentID,p.nvReference,pt.nvPaymentType,p.iAmount,m.nvMethod,u.nvUsers,p.tUpdateTime FROM Payment p, tblPaymentType pt, tblPaymentMethod m, tblUsers u WHERE p.nvReference = @reference and p.iPaymentTypeID = pt.iPaymentTypeID and p.iMethodID = m.iMethodID and p.iUsersID = u.iUsersID END payment.cs using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data; using System.Data.SqlClient; using System.Windows.Forms; namespace Finance { class payment { string connection = global::Finance.Properties.Settings.Default.PaymentConnectionString; #region Fields int _paymentid = 0; string _reference = string.Empty; string _paymenttype; double _amount = 0; string _paymentmethod; string _employeename; DateTime _updatetime = DateTime.Now; #endregion #region Properties public int paymentid { get { return _paymentid; } set { _paymentid = value; } } public string reference { get { return _reference; } set { _reference = value; } } public string paymenttype { get { return _paymenttype; } set { _paymenttype = value; } } public string paymentmethod { get { return _paymentmethod; } set { _paymentmethod = value; } } public double amount { get { return _amount;} set { _amount = value; } } public string employeename { get { return _employeename; } set { _employeename = value; } } public DateTime updatetime { get { return _updatetime; } set { _updatetime = value; } } #endregion #region Constructor public payment() { } public payment(string refer) { reference = refer; } public payment(int paymentID, string Reference, string Paymenttype, double Amount, string Paymentmethod, string Employeename, DateTime Time) { paymentid = paymentID; reference = Reference; paymenttype = Paymenttype; amount = Amount; paymentmethod = Paymentmethod; employeename = Employeename; updatetime = Time; } #endregion #region Methods public void Save() { try { SqlConnection connect = new SqlConnection(connection); SqlCommand command = new SqlCommand("payment_create", connect); command.CommandType = CommandType.StoredProcedure; command.Parameters.Add(new SqlParameter("@reference", reference)); command.Parameters.Add(new SqlParameter("@paymenttype", paymenttype)); command.Parameters.Add(new SqlParameter("@amount", amount)); command.Parameters.Add(new SqlParameter("@paymentmethod", paymentmethod)); command.Parameters.Add(new SqlParameter("@employeename", employeename)); command.Parameters.Add(new SqlParameter("@updatetime", updatetime)); connect.Open(); command.ExecuteScalar(); connect.Close(); } catch { } } public void Load(string reference) { try { SqlConnection connect = new SqlConnection(connection); SqlCommand command = new SqlCommand("Payment_Join", connect); command.CommandType = CommandType.StoredProcedure; command.Parameters.Add(new SqlParameter("@Reference", reference)); //MessageBox.Show("ref = " + reference); connect.Open(); SqlDataReader reader = command.ExecuteReader(); while (reader.Read()) { this.reference = Convert.ToString(reader["nvReference"]); // MessageBox.Show(reference); // MessageBox.Show("here"); // MessageBox.Show("payment type id = " + reader["nvPaymentType"]); // MessageBox.Show("here1"); this.paymenttype = Convert.ToString(reader["nvPaymentType"]); // MessageBox.Show(paymenttype.ToString()); this.amount = Convert.ToDouble(reader["iAmount"]); this.paymentmethod = Convert.ToString(reader["nvMethod"]); this.employeename = Convert.ToString(reader["nvUsers"]); this.updatetime = Convert.ToDateTime(reader["tUpdateTime"]); } reader.Close(); } catch (Exception ex) { MessageBox.Show("Check it again" + ex); } } #endregion } } i have already binded the combo box items through designer, When i run the application i just get the reference populated in form 2 and combo box just populated not the particular value which is fetched. New to c# so help me to get familiar

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  • Accessing both stored procedure output parameters AND the result set in Entity Framework?

    - by MS.
    Is there any way of accessing both a result set and output parameters from a stored procedure added in as a function import in an Entity Framework model? I am finding that if I set the return type to "None" such that the designer generated code ends up calling base.ExecuteFunction(...) that I can access the output parameters fine after calling the function (but of course not the result set). Conversely if I set the return type in the designer to a collection of complex types then the designer generated code calls base.ExecuteFunction<T>(...) and the result set is returned as ObjectResult<T> but then the value property for the ObjectParameter instances is NULL rather than containing the proper value that I can see being passed back in Profiler. I speculate the second method is perhaps calling a DataReader and not closing it. Is this a known issue? Any work arounds or alternative approaches? Edit My code currently looks like public IEnumerable<FooBar> GetFooBars( int? param1, string param2, DateTime from, DateTime to, out DateTime? createdDate, out DateTime? deletedDate) { var createdDateParam = new ObjectParameter("CreatedDate", typeof(DateTime)); var deletedDateParam = new ObjectParameter("DeletedDate", typeof(DateTime)); var fooBars = MyContext.GetFooBars(param1, param2, from, to, createdDateParam, deletedDateParam); createdDate = (DateTime?)(createdDateParam.Value == DBNull.Value ? null : createdDateParam.Value); deletedDate = (DateTime?)(deletedDateParam.Value == DBNull.Value ? null : deletedDateParam.Value); return fooBars; }

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  • Subsonic SELECT FROM msdb

    - by Lukasz Lysik
    Hi, I want to execute the following query using Subsonic: SELECT MAX([restore_date]) FROM [msdb].[dbo].[restorehistory] While the aggregate part is easy for me, the problem is with the name of the table. How should I force Subsonic to select from different database than default one.

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  • performance issue: difference between select s.* vs select *

    - by kamil
    Recently I had some problem in performance of my query. The thing is described here: poor Hibernate select performance comparing to running directly - how debug? After long time of struggling, I've finally discovered that the query with select prefix like: select sth.* from Something as sth... Is 300x times slower then query started this way: select * from Something as sth.. Could somebody help me, and asnwer why is that so? Some external documents on this would be really useful. The table used for testing was: SALES_UNIT table contains some basic info abot sales unit node such as name and etc. The only association is to table SALES_UNIT_TYPE, as ManyToOne. The primary key is ID and field VALID_FROM_DTTM which is date. SALES_UNIT_RELATION contains relation PARENT-CHILD between sales unit nodes. Consists of SALES_UNIT_PARENT_ID, SALES_UNIT_CHILD_ID and VALID_TO_DTTM/VALID_FROM_DTTM. No association with any tables. The PK here is ..PARENT_ID, ..CHILD_ID and VALID_FROM_DTTM The actual query I've done was: select s.* from sales_unit s left join sales_unit_relation r on (s.sales_unit_id = r.sales_unit_child_id) where r.sales_unit_child_id is null select * from sales_unit s left join sales_unit_relation r on (s.sales_unit_id = r.sales_unit_child_id) where r.sales_unit_child_id is null Same query, both uses left join and only difference is with select.

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  • Getting "too many rows" error inside a "for" cursor loop

    - by Will
    I have a trigger that contains two cursors loops, one nested inside the other like this: FOR outer_rec IN outer_cursor LOOP FOR inner_rec IN inner_cursor LOOP -- Do some calculations END LOOP; END LOOP; Somewhere in this it is throwing the following error: ORA-01422: exact fetch returns more than requested number of rows I've been trying to determine where it's coming from for an hour or so.. but should this error never happen? Also.. I am assuming the inner loop automatically closes and opens itself again every time the outer loop goes the next record, i hope this is correct.

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  • Is count(*) really expensive ?

    - by Anil Namde
    I have a page where I have 4 tabs displaying 4 different reports based off different tables. I obtain the row count of each table using a select count(*) from <table> query and display number of rows available in each table on the tabs. As a result, each page postback causes 5 count(*) queries to be executed (4 to get counts and 1 for pagination) and 1 query for getting the report content. Now my question is: are count(*) queries really expensive -- should I keep the row counts (at least those that are displayed on the tab) in the view state of page instead of querying multiple times? How expensive are COUNT(*) queries ?

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  • How can I use an array within a SQL query

    - by ThinkingInBits
    So I'm trying to take a search string (could be any number of words) and turn each value into a list to use in the following IN statement) in addition, I need a count of all these values to use with my having count filter $search_array = explode(" ",$this->search_string); $tag_count = count($search_array); $db = Connect::connect(); $query = "select p.id from photographs p left join photograph_tags c on p.id = c.photograph_id and c.value IN ($search_array) group by p.id having count(c.value) >= $tag_count"; This currently returns no results, any ideas?

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  • How to avoid geometric slowdown with large Linq transactions?

    - by Shaul
    I've written some really nice, funky libraries for use in LinqToSql. (Some day when I have time to think about it I might make it open source... :) ) Anyway, I'm not sure if this is related to my libraries or not, but I've discovered that when I have a large number of changed objects in one transaction, and then call DataContext.GetChangeSet(), things start getting reaalllly slooowwwww. When I break into the code, I find that my program is spinning its wheels doing an awful lot of Equals() comparisons between the objects in the change set. I can't guarantee this is true, but I suspect that if there are n objects in the change set, then the call to GetChangeSet() is causing every object to be compared to every other object for equivalence, i.e. at best (n^2-n)/2 calls to Equals()... Yes, of course I could commit each object separately, but that kinda defeats the purpose of transactions. And in the program I'm writing, I could have a batch job containing 100,000 separate items, that all need to be committed together. Around 5 billion comparisons there. So the question is: (1) is my assessment of the situation correct? Do you get this behavior in pure, textbook LinqToSql, or is this something my libraries are doing? And (2) is there a standard/reasonable workaround so that I can create my batch without making the program geometrically slower with every extra object in the change set?

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  • how to do multi insert and obtain ids

    - by liysd
    hi, I want to insert some data into a table (id PK autoincrement, val) with use multi insert INSERT INTO tab (val) VALUES (1), (2), (3) Is it possible to obtain a table of last inserted ids? I'm asking becouse I'm not sure if all will in this form: (n, n+1, n+2). I use mysql inodb.

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  • getting complete sql query in jython

    - by kdev
    result=sqlstring.executeQuery("select distinct table_name,owner from all_tables ") rs.append(str(i)+' , '+result.getString("table_name")+' , '+result.getString("owner")) If i want to display the query select * from all_tables or ' select count(*) from all_tables' how can i get the output to display . Please suggest thanks

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  • Select rows where column LIKE dictionary word

    - by Gerve
    I have 2 tables: Dictionary - Contains roughly 36,000 words CREATE TABLE IF NOT EXISTS `dictionary` ( `word` varchar(255) NOT NULL, PRIMARY KEY (`word`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; Datas - Contains roughly 100,000 rows CREATE TABLE IF NOT EXISTS `datas` ( `ID` int(11) NOT NULL AUTO_INCREMENT, `hash` varchar(32) NOT NULL, `data` varchar(255) NOT NULL, `length` int(11) NOT NULL, `time` int(11) NOT NULL, PRIMARY KEY (`ID`), UNIQUE KEY `hash` (`hash`), KEY `data` (`data`), KEY `length` (`length`), KEY `time` (`time`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=105316 ; I would like to somehow select all the rows from datas where the column data contains 1 or more words. I understand this is a big ask, it would need to match all of these rows together in every combination possible, so it needs the best optimization. I have tried the below query, but it just hangs for ages: SELECT `datas`.*, `dictionary`.`word` FROM `datas`, `dictionary` WHERE `datas`.`data` LIKE CONCAT('%', `dictionary`.`word`, '%') AND LENGTH(`dictionary`.`word`) > 3 ORDER BY `length` ASC LIMIT 15 I have also tried something similar to the above with a left join, and on clause that specified the like statement.

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  • Get count matches in query on large table very slow

    - by Roy Roes
    I have a mysql table "items" with 2 integer fields: seid and tiid The table has about 35000000 records, so it's very large. seid tiid ----------- 1 1 2 2 2 3 2 4 3 4 4 1 4 2 The table has a primary key on both fields, an index on seid and an index on tiid. Someone types in 1 or more tiid values and now I would like to get the seid with most results. For example when someone types 1,2,3, I would like to get seid 2 and 4 as result. They both have 2 matches on the tiid values. My query so far: SELECT COUNT(*) as c, seid FROM items WHERE tiid IN (1,2,3) GROUP BY seid HAVING c = (SELECT COUNT(*) as c, seid FROM items WHERE tiid IN (1,2,3) GROUP BY seid ORDER BY c DESC LIMIT 1) But this query is extremly slow, because of the large table. Does anyone know how to construct a better query for this purpose?

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  • how do I integrate the aspnet_users table (asp.net membership) into my existing database

    - by ooo
    i have a database that already has a users table COLUMNS: userID - int loginName - string First - string Last - string i just installed the asp.net membership table. Right now all of my tables are joined into my users table foreign keyed into the "userId" field How do i integrate asp.net_users table into my schema? here are the ideas i thought of: Add a membership_id field to my users table and on new inserts, include that new field in my users table. This seems like the cleanest way as i dont need to break any existing relationships. break all existing relationship and move all of the fields in my user table into the asp.net_users table. This seems like a pain but ultimately will lead to the most simple, normalized solution any thoughts?

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  • I want to do a sql update loop statement, by using the do--while in php

    - by Jean
    Hello, I want to loop the update statement, but it only loops once. Here is the code I am using: do { mysql_select_db($database_ll, $ll); $query_query= "update table set ex='$71[1]' where field='val'"; $query = mysql_query($query_query, $ll) or die(mysql_error()); $row_domain_all = mysql_fetch_assoc($query); } while ($row_query = mysql_fetch_assoc($query)); Thanks Jean

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  • Database design advice needed.

    - by user346271
    Hi all, I'm a lone developer for a telecoms company, and am after some database design advice from anyone with a bit of time to answer. I am inserting into one table ~2 million rows each day, these tables then get archived and compressed on a monthly basis. Each monthly table contains ~15,000,000 rows. Although this is increasing month on month. For every insert I do above I am combining the data from rows which belong together and creating another "correlated" table. This table is currently not being archived, as I need to make sure I never miss an update to the correlated table. (Hope that makes sense) Although in general this information should remain fairly static after a couple of days of processing. All of the above is working perfectly. However my company now wishes to perform some stats against this data, and these tables are getting too large to provide the results in what would be deemed a reasonable time. Even with the appropriate indexes set. So I guess after all the above my question is quite simple. Should I write a script which groups the data from my correlated table into smaller tables. Or should I store the queries result sets in something like memcache? I'm already using mysqls cache, but due to having limited control over how long the data is stored for, it's not working ideally. The main advantages I can see of using something like memcache: No blocking on my correlated table after the query has been cashed. Greater flexibility of sharing the collected data between the backend collector and front end processor. (i.e custom reports could be written in the backend and the results of these stored in the cache under a key which then gets shared with anyone who would want to see the data of this report) Redundancy and scalability if we start sharing this data with a large amount of customers. The main disadvantages I can see of using something like memcache: Data is not persistent if machine is rebooted / cache is flushed. The main advantages of using MySql Persistent data. Less code changes (although adding something like memcache is trivial anyway) The main disadvantages of using MySql Have to define table templates every time I want to store provide a new set of grouped data. Have to write a program which loops through the correlated data and fills these new tables. Potentially will still grow slower as the data continues to be filled. Apologies for quite a long question. It's helped me to write down these thoughts here anyway, and any advice/help/experience with dealing with this sort of problem would be greatly appreciated. Many thanks. Alan

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  • PHP MSSQL : How to display output when query return no row

    - by vamps
    i have a problem with my PHP-MSSQL query. i have a join table that need to give a result something be like this: Department Group A Group B Total A+B WORKHOUR A OTHOUR A WORKHOUR B OTHOUR B WORKHOUR OTHOUR HR 10 15 25 0 35 15 IT 5 5 5 5 Admin 12 12 12 12 the query will count how many employee as per given date (admin will enter data and once submitted, the query will give the above result). The problem is, the final output is a mess when there's no row to be displayed. the column is shifted to the right. i.e: only Group A in IT only Group B in Admin Department Group A Group B Total A+B WORKHOUR A OTHOUR A WORKHOUR B OTHOUR B WORKHOUR OTHOUR HR 10 15 25 0 35 15 IT 5 5 5 5 Admin 12 12 12 12 my question is, how to prevent this to happen? i've tried everything with While.... if else.. but the result is still the same. how to display output "0" if no rows to return? echo "0"; this is my QUERY: select DD.DPT_ID,DPT.DEPARTMENT_NAME,TU.EMP_GROUP, sum(DD.WORK_HOUR) AS WORK_HOUR, sum(DD.OT_HOUR) AS OT_HOUR FROM DEPARTMENT_DETAIL DD left join DEPARTMENT DPT ON (DD.DEPT_ID=DPT.DEPT_ID) LEFT JOIN TBL_USERS TU ON (TU.EMP_ID=DD.EMP_ID) WHERE DD_DATE>='2012-01-01' AND DD_DATE<='2012-01-31' AND TU.EMP_GROUP!=2 GROUP BY DD.DEPT_ID, DPT.DEPARTMENT_NAME,TU.EMP_GROUP ORDER BY DPT.DEPARTMENT_NAME this is one of the logic that i've used, but doesn't return the result that i want:: while($row = mssql_fetch_array($displayResult)) { if ((!$row["WORK_HOUR"])&&(!$row["OT_HOUR"])) { echo "<td >"; echo "empty"; echo "&nbsp;</td>"; echo "<td >"; echo "empty"; echo "&nbsp;</td>"; } else { echo "<td>"; echo $row["WORK_HOUR"]; echo "&nbsp;</td>"; echo "<td>"; echo $row["OT_HOUR"]; echo "&nbsp;</td>"; } } please help. i've been doing this for 2 days. @__@

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  • Extract time part from TimeStamp column in ORACLE

    - by RRUZ
    Actually i' am using MyTimeStampField-TRUNC(MyTimeStampField) to extract the time part from an timestamp column in Oracle. SELECT CURRENT_TIMESTAMP-TRUNC(CURRENT_TIMESTAMP) FROM DUAL this return +00 13:12:07.100729 this work ok for me, to extract the time part from an timestamp field, but i' m wondering if exist a better way (may be using an built-in function of ORACLE) to do this? Thanks.

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  • Which MySql line is faster:

    - by Camran
    I have a classified_id variable which matches one document in a MySql table. I am currently fetching the information about that one record like this: SELECT * FROM table WHERE table.classified_id = $classified_id I wonder if there is a faster approach, for example like this: SELECT 1 FROM table WHERE table.classified_id = $classified_id Wont the last one only select 1 record, which is exactly what I need, so that it doesn't have to scan the entire table but instead stops searching for records after 1 is found? Or am I dreaming this? Thanks

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