where-clause

问题 I have one table where date column is having data in below format: "7/25/2014 12:14:27 AM'. I need to fetch this date by putting in the where clause. can anyone suggest how can i do this? 回答1: Dates (stored in tables) are represented by 7 bytes - they do not have any format associated with them. If they are formatted as a string then that is the client program which you are using to access the database applying its own formatting to the date (which you can usually set via the preferences in

问题 I have one table where date column is having data in below format: "7/25/2014 12:14:27 AM'. I need to fetch this date by putting in the where clause. can anyone suggest how can i do this? 回答1: Dates (stored in tables) are represented by 7 bytes - they do not have any format associated with them. If they are formatted as a string then that is the client program which you are using to access the database applying its own formatting to the date (which you can usually set via the preferences in

问题 I have the following sample of code: {-# LANGUAGE ScopedTypeVariables #-} main = do putStrLn "Please input a number a: " a :: Int <- readLn print a putStrLn "Please input a number b: " b :: Int <- readLn print b putStrLn ("a+b+b^2:" ++ (show $ a+b+c)) where c = b^2 For some reason I cannot use variable b in a where clause, the error I get is the following: Main3.hs:13:15: error: Variable not in scope: b | 13 | where c = b^2 | ^ Any ideas how to make b available in the where clause? 回答1: Use

问题 Table A structure: Table B structure: Above are two tables, TableB.TableARelationID is a relationID which used to map table A. Desired output: The desired result would be taking TableA.RecordID and TableB.Text, but only of Type 2 in table B, i.e. ignore Type 1 Below is the SQL query which I used: SELECT tablea.recordid, tableb.text FROM tablea LEFT JOIN tableb ON tablea.relationid = tableb.tablearelationid WHERE type = 2 But the above query would output: i.e. RecordID 1 was missing, as the

问题 Table A structure: Table B structure: Above are two tables, TableB.TableARelationID is a relationID which used to map table A. Desired output: The desired result would be taking TableA.RecordID and TableB.Text, but only of Type 2 in table B, i.e. ignore Type 1 Below is the SQL query which I used: SELECT tablea.recordid, tableb.text FROM tablea LEFT JOIN tableb ON tablea.relationid = tableb.tablearelationid WHERE type = 2 But the above query would output: i.e. RecordID 1 was missing, as the

问题 My question is quiet simple: How to optimize the following query to not get performance issues once the database is growing: def projects_not_participating @project = Project.all - Project.joins(:participants).where(participant: {id: current_user.id}) end My model setup is this: def Project has_many :assignments has_many :participants, through: :assignments end def Participant has_many :assignments has_many :projects, through: assignments end I tried using Project.joins(:participant).where

问题 how to deal with NULL value in mysql where in CLAUSE i try like SELECT * FROM mytable WHERE field IN(1,2,3,NULL) it not working only work like : SELECT * FROM mytable WHERE field IN(1,2,3) OR field IS NULL how can i get it work in WHERE IN ? it is possible ? 回答1: As by my understanding you want to pull every record with 1,2,3 and null value. I don't think its possible to put null in the IN operator. Its expects values and null is well.. not a value. So You really have to put the OR with the

问题 I have the following result set which I get from SQL Server: employeeNumber | start_date | start_time | end_date | end_time ---------------+------------+------------+--------------+---------- 123 | 10-03-2020 | 18:13:55 | 10-03-2020 | 22:59:46 123 | 10-03-2020 | 18:24:22 | 10-03-2020 | 22:59:51 123 | 10-03-2020 | 23:24:22 | 10-03-2020 | 23:59:51 123 | 11-03-2020 | 18:25:25 | 11-03-2020 | 20:59:51 123 | 12-03-2020 | 18:40:22 | 12-03-2020 | 22:59:52 For some cases I have multiple rows for the

问题 Hello? I'm building an app using the flutter provider pattern. And I created a process to query the values ​​inside the object. I also have data in my model dart file. Check the code below. List<Device> _devices = [ Device(one: 'apple', two: 'iphone'), Device(one: 'samsung', two: 'galaxy') ]; String Query(String value) { return _media.where((medium) => medium.one == value) .map((medium) => (medium.two)).toString(); Query("apple") So, when I call that function, I expect iphone to be returned.

问题 Hello? I'm building an app using the flutter provider pattern. And I created a process to query the values ​​inside the object. I also have data in my model dart file. Check the code below. List<Device> _devices = [ Device(one: 'apple', two: 'iphone'), Device(one: 'samsung', two: 'galaxy') ]; String Query(String value) { return _media.where((medium) => medium.one == value) .map((medium) => (medium.two)).toString(); Query("apple") So, when I call that function, I expect iphone to be returned.