database-table

问题 Qt has built-in PDF export support ( QPrinter::PdfFormat ). What's the best way to print an SQL table to a PDF file? (a table from a database loaded with QSqlDatabase and linked to a QTableView )... 回答1: You use QWidget::render. See the documentation about Printing Widgets. 来源： https://stackoverflow.com/questions/5939491/qt4-print-a-sql-table-to-pdf

问题 In a MySQL script you can write: CREATE TABLE IF NOT EXISTS foo ...; ... other stuff ... and then you can run the script many times without re-creating the table. How do you do this in PostgreSQL? 回答1: This feature has been implemented in Postgres 9.1: CREATE TABLE IF NOT EXISTS myschema.mytable (i integer); For older versions , here is a function to work around it: CREATE OR REPLACE FUNCTION create_mytable () RETURNS void AS $func$ BEGIN IF EXISTS (SELECT FROM pg_catalog.pg_tables WHERE

问题 I'm looking for a way to find the row count for all my tables in Postgres. I know I can do this one table at a time with: SELECT count(*) FROM table_name; but I'd like to see the row count for all the tables and then order by that to get an idea of how big all my tables are. 回答1: There's three ways to get this sort of count, each with their own tradeoffs. If you want a true count, you have to execute the SELECT statement like the one you used against each table. This is because PostgreSQL

问题 I have to decide on design of my database for my application. So far I have Users table that stores these fields: **USERS** RecID - auto increment UserID - unique id (Primary key) UserName Password Salt TempPassword FirstName LastName Email SystemAdmin QuestionID Answer Active CreateDate CreateUID This table stores all information about users. There is another section in the app named Staff. According to the specs they want to see on the form **STAFF** First name Last name Middle Initial

问题 I'm looking for a way to find the row count for all my tables in Postgres. I know I can do this one table at a time with: SELECT count(*) FROM table_name; but I'd like to see the row count for all the tables and then order by that to get an idea of how big all my tables are. 回答1: There's three ways to get this sort of count, each with their own tradeoffs. If you want a true count, you have to execute the SELECT statement like the one you used against each table. This is because PostgreSQL

问题 I am trying to come up with an insert sql stament that will insert data from a table into another existing table. There are in fact some ways of doing this but I did not find a way that matches my requirements. I need an insert statement type query that will insert data into another table but it does not knows which headers both table have. For instance the origin table has 25 headers and the target one has 20, which 10 of them match in name. I would like to transfer the ones that are

问题 I am creating a database table for investigations and i need to log the person who reported the incident, this could be a record from the supplier or user tables. The easiest way to do this would be to have both a suppleir and a user id column in my investigations table but that seems wrong, what's a better way to do this? Thank you. 回答1: You could have another two tables - IncidentsReportedBySupplier (IncidentID, SupplierID) and IncidentsReportedByUser (IncidentID, UserID) - which would

问题 What I have: The next structure: table_zero -> id (PRIMARY with auto increment) -> other table_1 -> id (foreign key to table zero id) -> varchar(80) Example value: (aahellobbb) -> one_field table_2 -> id (foreign key to table zero id) -> varchar(160) Example value: (aaececehellobbb) -> other_field What I want: Search and get an (id,varchar) array containing all matches with the LIKE '%str%' on the varchar field. For example, if I search with the "hello" string, then I should get both example

问题 I use Squirrel SQL to connect to a JavaDB/Derby database on my desktop. I can run SQL queries. But how can I list all tables in the database? And preferably all column and column types. 回答1: You can do it easily from the GUI. After you open your session, click the Objects tab, then expand the tree. Expand the db, schema, and then table nodes, and you'll see all of your tables. If you click on a particular table node, a table will open to the right. By clicking the Columns tab, you can get the

问题 I ultimately what I needed is generic function which would take two datatable and and 2 tablekeys and return Joined datatable. So here is my first step to solve it. How Can I write Linq example of following T-SQL example in VB? SELECT * FROM Table1 LEFT OUTER JOIN Table2 ON Table1.key = Table2.key 回答1: It would be something like this: Dim JoinedResult = From t1 In Table1 Group Join t2 In Table2 On t1.key Equals t2.key Into RightTableResults = Group From t2 In RightTableResults.DefaultIfEmpty