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  • Representing Sparse Data in PostgreSQL

    - by Chris S
    What's the best way to represent a sparse data matrix in PostgreSQL? The two obvious methods I see are: Store data in a single a table with a separate column for every conceivable feature (potentially millions), but with a default value of NULL for unused features. This is conceptually very simple, but I know that with most RDMS implementations, that this is typically very inefficient, since the NULL values ususually takes up some space. However, I read an article (can't find its link unfortunately) that claimed PG doesn't take up data for NULL values, making it better suited for storing sparse data. Create separate "row" and "column" tables, as well as an intermediate table to link them and store the value for the column at that row. I believe this is the more traditional RDMS solution, but there's more complexity and overhead associated with it. I also found PostgreDynamic, which claims to better support sparse data, but I don't want to switch my entire database server to a PG fork just for this feature. Are there any other solutions? Which one should I use?

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  • Embedding generic sql queries into c# program

    - by Pooja Balkundi
    Okay referring to my first question code in the main, I want the user to enter employee name at runtime and then i take this name which user has entered and compare it with the e_name of my emp table , if it exists i want to display all information of that employee , how can I achieve this ? using System; using System.Collections.Generic; using System.Linq; using System.Windows.Forms; using MySql.Data.MySqlClient; namespace ConnectCsharppToMySQL { public class DBConnect { private MySqlConnection connection; private string server; private string database; private string uid; private string password; string name; //Constructor public DBConnect() { Initialize(); } //Initialize values private void Initialize() { server = "localhost"; database = "test"; uid = "root"; password = ""; string connectionString; connectionString = "SERVER=" + server + ";" + "DATABASE=" + database + ";" + "UID=" + uid + ";" + "PASSWORD=" + password + ";"; connection = new MySqlConnection(connectionString); } //open connection to database private bool OpenConnection() { try { connection.Open(); return true; } catch (MySqlException ex) { //When handling errors, you can your application's response based //on the error number. //The two most common error numbers when connecting are as follows: //0: Cannot connect to server. //1045: Invalid user name and/or password. switch (ex.Number) { case 0: MessageBox.Show("Cannot connect to server. Contact administrator"); break; case 1045: MessageBox.Show("Invalid username/password, please try again"); break; } return false; } } //Close connection private bool CloseConnection() { try { connection.Close(); return true; } catch (MySqlException ex) { MessageBox.Show(ex.Message); return false; } } //Insert statement public void Insert() { string query = "INSERT INTO emp (e_name, age) VALUES('Pooja R', '21')"; //open connection if (this.OpenConnection() == true) { //create command and assign the query and connection from the constructor MySqlCommand cmd = new MySqlCommand(query, connection); //Execute command cmd.ExecuteNonQuery(); //close connection this.CloseConnection(); } } //Update statement public void Update() { string query = "UPDATE emp SET e_name='Peachy', age='22' WHERE e_name='Pooja R'"; //Open connection if (this.OpenConnection() == true) { //create mysql command MySqlCommand cmd = new MySqlCommand(); //Assign the query using CommandText cmd.CommandText = query; //Assign the connection using Connection cmd.Connection = connection; //Execute query cmd.ExecuteNonQuery(); //close connection this.CloseConnection(); } } //Select statement public List<string>[] Select() { string query = "SELECT * FROM emp where e_name=(/*I WANT USER ENTERED NAME TO GET INSERTED HERE*/)"; //Create a list to store the result List<string>[] list = new List<string>[3]; list[0] = new List<string>(); list[1] = new List<string>(); list[2] = new List<string>(); //Open connection if (this.OpenConnection() == true) { //Create Command MySqlCommand cmd = new MySqlCommand(query, connection); //Create a data reader and Execute the command MySqlDataReader dataReader = cmd.ExecuteReader(); //Read the data and store them in the list while (dataReader.Read()) { list[0].Add(dataReader["e_id"] + ""); list[1].Add(dataReader["e_name"] + ""); list[2].Add(dataReader["age"] + ""); } //close Data Reader dataReader.Close(); //close Connection this.CloseConnection(); //return list to be displayed return list; } else { return list; } } public static void Main(String[] args) { DBConnect db1 = new DBConnect(); Console.WriteLine("Initializing"); db1.Initialize(); Console.WriteLine("Search :"); Console.WriteLine("Enter the employee name"); db1.name = Console.ReadLine(); db1.Select(); Console.ReadLine(); } } }

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  • Wiki Database, is there one?

    - by Faiz
    I was searching the net for something like a wiki database, just like wikipedia but instead stores structured content, editable by users. What I was looking for was an online database accessible by everyone where people can design the schema and data with proper versioning of both schema and data. I couldn't find any such site. I am not sure if it is my search skills or if there really is no wiki database as of now. Does anyone out there know anything like this? I think there is a great potential for something like this. A possible example will be a website with a GUI for querying a MySQL DB where any website visitor can create DB objects and populate data.

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  • SSIS(sql server integration service) xml data flow

    - by swapna
    Hi, I have an xml file the content which i have to write to a Database table using ssis pacakge. I am using xml source nad oledb destination My issue now is this xml file generate multiple outputs .(event,produt,offer,form) etc. But i need to write all in one data row(more than one if 2 products are there for the event) in the database. But i do not know how to use this multiple outputs and make a single row for a event. I hav read numerous articles about this subject but not able to take a decision.what is the right way of doing this. 1) xml source ? (if i use this how do i merge the multiple outputs) 2) or a script task using xml objects read and write to the DB. or anything new ? Please provide me some solutions xml sample file * - ABc. 2009-06-07 2010-04-30 region test 1 contact - offertest product1 product1 187 * Thanks SNA

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  • Problem with interface implementation in partial classes.

    - by Bas
    I have a question regarding a problem with L2S, Autogenerated DataContext and the use of Partial Classes. I have abstracted my datacontext and for every table I use, I'm implementing a class with an interface. In the code below you can see I have the Interface and two partial classes. The first class is just there to make sure the class in the auto-generated datacontext inherets Interface. The other autogenerated class makes sure the method from Interface is implemented. namespace PartialProject.objects { public interface Interface { Interface Instance { get; } } //To make sure the autogenerated code inherits Interface public partial class Class : Interface { } //This is autogenerated public partial class Class { public Class Instance { get { return this.Instance; } } } } Now my problem is that the method implemented in the autogenerated class gives the following error: - Property 'Instance' cannot implement property from interface 'PartialProject.objects.Interface'. Type should be 'PartialProjects.objects.Interface'. <- Any idea how this error can be resolved? Keep in mind that I can't edit anything in the autogenerated code. Thanks in advance!

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  • How do I perform a batch insert in Django?

    - by Thierry Lam
    In mysql, you can insert multiple rows to a table in one query for n 0: INSERT INTO tbl_name (a,b,c) VALUES(1,2,3),(4,5,6),(7,8,9), ..., (n-2, n-1, n); Is there a way to achieve the above with Django queryset methods? Here's an example: values = [(1, 2, 3), (4, 5, 6), ...] for value in values: SomeModel.objects.create(first=value[0], second=value[1], third=value[2]) I believe the above is calling an insert query for each iteration of the for loop. I'm looking for a single query, is that possible in Django?

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  • How can I adjust the CommandTImeout in DbFit for long running queries?

    - by Ben Farmer
    Is there any way to increase the CommandTimeout for DbFit queries? I have a long running stored procedure that times out when running it in a DbFit Test. It's possible for the procedure to run for a really long time (processing millions of records) and would like to have DbFit wait until it's completed, even if it takes several minutes. We are using the latest version of FitSharp (downloaded it yesterday) and use the version of DbFit that is included with FitSharp.

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  • Integer comparison as string

    - by J Pollack
    Hi I have an integer column and I want to find numbers that start with specific digits. For example they do match if I look for '123': 1234567 123456 1234 They do not match: 23456 112345 0123445 Is the only way to handle the task by converting the Integers into Strings before doing string comparison? Also I am using Postgre regexp_replace(text, pattern, replacement) on numbers which is very slow and inefficient way doing it. The case is that I have large amount of data to handle this way and I am looking for the most economical way doing this.

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  • MySQL table data transformation -- how can I dis-aggregate MySQL time data?

    - by lighthouse65
    We are coding for a MySQL data warehousing application that stores descriptive data (User ID, Work ID, Machine ID, Start and End Time columns in the first table below) associated with time and production quantity data (Output and Time columns in the first table below) upon which aggregate (SUM, COUNT, AVG) functions are applied. We now wish to dis-aggregate time data for another type of analysis. Our current data table design: +---------+---------+------------+---------------------+---------------------+--------+------+ | User ID | Work ID | Machine ID | Event Start Time | Event End Time | Output | Time | +---------+---------+------------+---------------------+---------------------+--------+------+ | 080025 | ABC123 | M01 | 2008-01-24 16:19:15 | 2008-01-24 16:34:45 | 2120 | 930 | +---------+---------+------------+---------------------+---------------------+--------+------+ Reprocessing dis-aggregation that we would like to do would be to transform table content based on a granularity of minutes, rather than the current production event ("Event Start Time" and "Event End Time") granularity. The resulting reprocessing of existing table rows would look like: +---------+---------+------------+---------------------+--------+ | User ID | Work ID | Machine ID | Production Minute | Output | +---------+---------+------------+---------------------+--------+ | 080025 | ABC123 | M01 | 2010-01-24 16:19 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:20 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:21 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:22 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:23 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:24 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:25 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:26 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:27 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:28 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:29 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:30 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:31 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:22 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:33 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:34 | 133 | +---------+---------+------------+---------------------+--------+ So the reprocessing would take an existing row of data created at the granularity of production event and modify the granularity to minutes, eliminating redundant (Event End Time, Time) columns while doing so. It assumes a constant rate of production and divides output by the difference in minutes plus one to populate the new table's Output column. I know this can be done in code...but can it be done entirely in a MySQL insert statement (or otherwise entirely in MySQL)? I am thinking of a INSERT ... INTO construction but keep getting stuck. An additional complexity is that there are hundreds of machines to include in the operation so there will be multiple rows (one for each machine) for each minute of the day. Any ideas would be much appreciated. Thanks.

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  • I need some help optimizing my database schema

    - by Steffan
    Here's a layout of my data: Heading 1: Sub heading Sub heading Sub heading Sub heading Sub heading Heading 2: Sub heading Sub heading Sub heading Sub heading Sub heading Heading 3: Sub heading Sub heading Sub heading Sub heading Sub heading Heading 4: Sub heading Sub heading Sub heading Sub heading Sub heading Heading 5: Sub heading Sub heading Sub heading Sub heading Sub heading These headings need to have a 'Completion Status' boolean value which gets linked to a user Id. Currently, this is how my table looks: id | userID | field_1 | field_2 | field_3 | field_4 | etc... ----------------------------------------------------------------------- 1 | 1 | 0 | 0 | 1 | 0 | ----------------------------------------------------------------------- 2 | 2 | 1 | 0 | 1 | 1 | Each field represents one Sub Heading. Having this many columns in my table looks awfully inefficient... How can I go about optimizing this? I can't think of any way to neaten it up :/

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  • Historical / auditable database

    - by Mark
    Hi all, This question is related to the schema that can be found in one of my other questions here. Basically in my database I store users, locations, sensors amongst other things. All of these things are editable in the system by users, and deletable. However - when an item is edited or deleted I need to store the old data; I need to be able to see what the data was before the change. There are also non-editable items in the database, such as "readings". They are more of a log really. Readings are logged against sensors, because its the reading for a particular sensor. If I generate a report of readings, I need to be able to see what the attributes for a location or sensor was at the time of the reading. Basically I should be able to reconstruct the data for any point in time. Now, I've done this before and got it working well by adding the following columns to each editable table: valid_from valid_to edited_by If valid_to = 9999-12-31 23:59:59 then that's the current record. If valid_to equals valid_from, then the record is deleted. However, I was never happy with the triggers I needed to use to enforce foreign key consistency. I can possibly avoid triggers by using the extension to the "PostgreSQL" database. This provides a column type called "period" which allows you to store a period of time between two dates, and then allows you to do CHECK constraints to prevent overlapping periods. That might be an answer. I am wondering though if there is another way. I've seen people mention using special historical tables, but I don't really like the thought of maintainling 2 tables for almost every 1 table (though it still might be a possibility). Maybe I could cut down my initial implementation to not bother checking the consistency of records that aren't "current" - i.e. only bother to check constraints on records where the valid_to is 9999-12-31 23:59:59. Afterall, the people who use historical tables do not seem to have constraint checks on those tables (for the same reason, you'd need triggers). Does anyone have any thoughts about this? PS - the title also mentions auditable database. In the previous system I mentioned, there is always the edited_by field. This allowed all changes to be tracked so we could always see who changed a record. Not sure how much difference that might make. Thanks.

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  • Using outer query result in a subquery in postgresql

    - by brad
    I have two tables points and contacts and I'm trying to get the average points.score per contact grouped on a monthly basis. Note that points and contacts aren't related, I just want the sum of points created in a month divided by the number of contacts that existed in that month. So, I need to sum points grouped by the created_at month, and I need to take the count of contacts FOR THAT MONTH ONLY. It's that last part that's tricking me up. I'm not sure how I can use a column from an outer query in the subquery. I tried something like this: SELECT SUM(score) AS points_sum, EXTRACT(month FROM created_at) AS month, date_trunc('MONTH', created_at) + INTERVAL '1 month' AS next_month, (SELECT COUNT(id) FROM contacts WHERE contacts.created_at <= next_month) as contact_count FROM points GROUP BY month, next_month ORDER BY month So, I'm extracting the actual month that my points are being summed, and at the same time, getting the beginning of the next_month so that I can say "Get me the count of contacts where their created at is < next_month" But it complains that column next_month doesn't exist This is understandable as the subquery knows nothing about the outer query. Qualifying with points.next_month doesn't work either. So can someone point me in the right direction of how to achieve this? Tables: Points score | created_at 10 | "2011-11-15 21:44:00.363423" 11 | "2011-10-15 21:44:00.69667" 12 | "2011-09-15 21:44:00.773289" 13 | "2011-08-15 21:44:00.848838" 14 | "2011-07-15 21:44:00.924152" Contacts id | created_at 6 | "2011-07-15 21:43:17.534777" 5 | "2011-08-15 21:43:17.520828" 4 | "2011-09-15 21:43:17.506452" 3 | "2011-10-15 21:43:17.491848" 1 | "2011-11-15 21:42:54.759225" sum, month and next_month (without the subselect) sum | month | next_month 14 | 7 | "2011-08-01 00:00:00" 13 | 8 | "2011-09-01 00:00:00" 12 | 9 | "2011-10-01 00:00:00" 11 | 10 | "2011-11-01 00:00:00" 10 | 11 | "2011-12-01 00:00:00"

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  • Failed to Kill Process in SQL 2008

    - by Andrea.Ko
    I have a process with the following information, and i execute the kill process to kill this id, and it return me "Only user processes can be killed." SPID:11 Status:BACKGROUND Login:sa HostName: . BlkBy: . DBName: SAFEMIG Command:CHECKPOINT Normally, all the session to login to this server, it should have a HostName which display our PC name, but this connection is with a dot, so not sure who is executing what process that have this connection. I execute "dbcc inputbuffer(11)" It return me"EventType= No Event, Parameters = 0 and EventInfo=Null" Appreciate for any help\advice on this problem!

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  • Conditional Join - join 1 tables 2 ways

    - by Jon H
    I have a set of (not very well normalised or relational) tables named PLAN, GROUP, PRODUCT CLIENT Most have linkage i.e. PLAN - CLIENT on clno GROUP to PRODUCT on PRODCD However, the linkage between PLAN and GROUP is tricky. A plan has 2 field of interest GRPNO and PRODCD. What I want to do is if GRPNO != 0 then join GROUP on GRPNO. However if GRPNO = 0 then I want to join GROUP on PRODCD. The frustrating thing is that the fileds I want to return in my queries are the same across the board I just need to be able to vary the join, or join the same table twice. The best I can come up with is 2 queries and merge them using datasets, or possibly using a union. Is there a nifty way to do this in one select? I should point out I am access Foxpro over ODBC to do this. Thank you!

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  • Date arithmetic using integer values

    - by Dave Jarvis
    Problem String concatenation is slowing down a query: date(extract(YEAR FROM m.taken)||'-1-1') d1, date(extract(YEAR FROM m.taken)||'-1-31') d2 This is realized in code as part of a string, which follows (where the p_ variables are integers): date(extract(YEAR FROM m.taken)||''-'||p_month1||'-'||p_day1||''') d1, date(extract(YEAR FROM m.taken)||''-'||p_month2||'-'||p_day2||''') d2 This part of the query runs in 3.2 seconds with the dates, and 1.5 seconds without, leading me to believe there is ample room for improvement. Question What is a better way to create the date (presumably without concatenation)? Many thanks!

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  • How to call a scalar function in a stored procedure

    - by Luke101
    I am wacking y head over the problem with this code. DECLARE @root hierarchyid declare @lastchild hierarchyid SELECT @root = NodeHierarchyID from NodeHierarchy where ID = 1 set @lastchild = getlastchild(@root) it says it does not recognize getlastchild function. What am I doing wrong here

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  • PostgreSQL JOIN with array type with array elements order, how to implement?

    - by Adiasz
    Hello I have two tables in database: CREATE TABLE items( id SERIAL PRIMARy KEY, ... some other fields ); This table contains come data row with unique ID. CREATE TABLE some_choosen_data_in_order( id SERIAL PRIMARy KEY, id_items INTEGER[], ); This table contains array type field. Each row contains values of IDs from table "items" in specyfic order. For example: {2,4,233,5}. Now, I want to get data from table "items" for choosen row from table "some_choosen_data_in_order" with order for elements in array type. The my attempt is JOIN: SELECT I.* FROM items AS I JOIN some_choosen_data_in_order AS S ON I.id = ANY(S.id_items) WHERE S.id = ? Second attempt was subquery like: SELECT I.* FROM items AS I WHERE I.id = ANY (ARRAY[SELECT S.id_items FROM some_choosen_data_in_order WHERE id = ?]) But none of them keep IDs order in array field. Could You help me, how to get data from "items" table with correspond with array IDs order from "some_choosen_data_in_order" table for specyfic row?

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  • Acquiring Table Lock in Database - Interview Question

    - by harigm
    One of my interview Questions, if multiple users across the world are accessing the application, in which it uses a Table which has a Primary Key as Auto Increment Field. The Question how can you prevent the other user getting the Same Primary key when the other user is executing? My answer was I will obtain the Lock on the table and I will make the user to wait Until that user is released with the Primary key. But the Question How do you acquire the Table lock programmatically and implement this? If there are 1000 users coming every minute to the application, if you explicity hold the lock on the table, then the application will become slower? How do you manage this? Please suggest the possible answers for the above question

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  • LINQ: Create persistable Associations in Code, Without Foreign Key

    - by Alex
    Hello, I know that I can create LINQ Associations without a Foreign Key. The problem is, I've been doing this by adding the [Association] attribute in the DBML file (same as through the designer), which will get erased again after I refresh my database (and reload the entire table structure). I know that there is the MyData.cs file (as part of the DBML) in which I can place my partial extensions etc. to domain objects (to persist even after I refresh the DBML), but I don't know how to create an association there?

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  • Why index_merge is not used here?

    - by user198729
    Setup: mysql> create table t(a integer unsigned,b integer unsigned); mysql> insert into t(a,b) values (1,2),(1,3),(2,4); mysql> create index i_t_a on t(a); mysql> create index i_t_b on t(b); mysql> explain select * from t where a=1 or b=4; +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | t | ALL | i_t_a,i_t_b | NULL | NULL | NULL | 3 | Using where | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ Is there something I'm missing?

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  • Help to choose NoSQL database for project

    - by potapuff
    There is a table: doc_id(integer)-value(integer) Approximate 100k doc_id and 27?? rows. Majority query on this table - searching documents similar to current document: select 10 documents with maximum of (count common to current document value)/(count ov values in document). Nowadays we use PostgreSQL. Table weight (with index) ~1,5 GB. Average query time ~0.5s. Should I transfer all this to NoSQL base, if so, what?

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  • LIKE operator with $variable

    - by skarama
    This is my first question here and I hope it is simple enough to get a quick answer! Basically, I have the following code: $variable = curPageURL(); $query = 'SELECT * FROM `tablename` WHERE `columnname` LIKE '$variable' ; If I echo the $variable, it prints the current page's url( which is a javascript on my page) Ultimately, what I want, is to be able to make a search for which the search-term is the current page's url, with wildcards before and after. I am not sure if this is possible at all, or if I simply have a syntax error, because I get no errors, simply no result! I tried : $query = 'SELECT * FROM `tablename` WHERE `columnname` LIKE '"echo $variable" ' ; But again, I'm probably missing or using a misplaced ' " ; etc. Please tell me what I'm doing wrong!

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  • Bus Timetable database design

    - by paddydub
    hi, I'm trying to design a db to store the timetable for 300 different bus routes, Each route has a different number of stops and different times for Monday-Friday, Saturday and Sunday. I've represented the bus departure times for each route as follows, I'm not sure if i should have null values in the table, does this look ok? route,Num,Day, t1, t2, t3, t4 t5 t6 t7 t8 t9 t10 117, 1, Monday, 9:00, 9:30, 10:50, 12:00, 14:00 18:00 19:00 null null null 117, 2, Monday, 9:03, 9:33, 10:53, 12:03, 14:03 18:03 19:03 null null null 117, 3, Monday, 9:06, 9:36, 10:56, 12:06, 14:06 18:06 19:06 null null null 117, 4, Monday, 9:09, 9:39, 10:59, 12:09, 14:09 18:09 19:09 null null null . . . 117, 20, Monday, 9:39, 10.09, 11:39, 12:39, 14:39 18:39 19:39 null null null 119, 1, Monday, 9:00, 9:30, 10:50, 12:00, 14:00 18:00 19:00 20:00 21:00 22:00 119, 2, Monday, 9:03, 9:33, 10:53, 12:03, 14:03 18:03 19:03 20:03 21:03 22:03 119, 3, Monday, 9:06, 9:36, 10:56, 12:06, 14:06 18:06 19:06 20:06 21:06 22:06 119, 4, Monday, 9:09, 9:39, 10:59, 12:09, 14:09 18:09 19:09 20:09 21:09 22:09 . . . 119, 37, Monday, 9:49, 9:59, 11:59, 12:59, 14:59 18:59 19:59 20:59 21:59 22:59 139, 1, Sunday, 9:00, 9:30, 20:00 21:00 22:00 null null null null null 139, 2, Sunday, 9:03, 9:33, 20:03 21:03 22:03 null null null null null 139, 3, Sunday, 9:06, 9:36, 20:06 21:06 22:06 null null null null null 139, 4, Sunday, 9:09, 9:39, 20:09 21:09 22:09 null null null null null . . . 139, 20, Sunday, 9:49, 9:59, 20:59 21:59 22:59 null null null null null

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