constraints

问题 Let say I have a large image (400wx700h) pixels. I want this image to be centered on the iphone and take 1/4 of the display area. Doesn't matter if is iphone 4 or iphone 6+, I still want this image to be centered and take only 1/4 of the display area. Also, I want to design this in storyboard and using constraints, with no coding. I know how to center the image, but not sure about the 1/4 portion. Can someone please guide me? Thanks Borna 回答1: Create constraints for equal width and height

问题 I have the following 3 tables: tblA ID - PK name tblB ID - PK tblAID - FK references tblA.ID pkID2 tblC ID - PK tblAID * fkID2 * ... I want to make this tuple a FK of (tblB.tblAID, tblB.pkID2) If I do this: alter table tblC with check add constraint FK_tblC_tblB foreign key (tblAID, fkID2) references tblB (tblAID, pkID2) I get an error message: There are no primary or candidate keys in the referenced table 'tblB' that match the referencing column list in the foreign key 'FK_tblC_tblB' I.e.: I

问题 There always be the error: "Cannot add foreign key constraint" when I create my last table . System: Mac OS X 10.9 DB : MySQL 5.6.14 DBM : Sequel Pro CREATE TABLE users ( uid INT AUTO_INCREMENT PRIMARY KEY, uname VARCHAR(20) NOT NULL, uemail VARCHAR(20) NOT NULL, ucity VARCHAR(20), upassw VARCHAR(20) NOT NULL ); CREATE TABLE songs( sid INT AUTO_INCREMENT PRIMARY KEY, sname VARCHAR(20) NOT NULL, srldate DATE NOT NULL ); CREATE TABLE albums ( albid INT AUTO_INCREMENT PRIMARY KEY, albname

问题 I asked about the minimum cost maximum flow several weeks ago. Kraskevich's answer was brilliant and solved my problem. I've implemented it and it works fine (available only in French, sorry). Additionaly, the algorithm can handle the assignement of i ( i > 1) projects to each student. Now I'm trying something more difficult. I'd like to add constraints on choices. In the case one wants to affect i ( i > 1) projects to each student, I'd like to be able to specify which projects are compatible

问题 I'm using Symfony 2 with Doctrine. I have 4 classes: Country, District, County and Local. District has a foreign key of Country; County has a foreign of District; Local has a foreign key of District. The problem is that when inserting a County (using data fixtures), I get the error SQLSTATE[23000]: Integrity constraint violation: I dumped the SQL to create the tables and constraints and got this: CREATE TABLE Country (id INT AUTO_INCREMENT NOT NULL, name VARCHAR(255) NOT NULL, insertedAt

问题 I'm building a pharmacy management application. Each Pharmacy requires an administrator. The constraints are like so: public class Pharmacy implements Serializable { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private int id; @NotNull private String name; @NotNull private String city; @NotNull private String streetAdress; @OneToOne private Stock stock; @NotNull @OneToOne private Administrator administrator; //... Notice how there's a not null constraint in the Administrator field.

问题 I'm building a pharmacy management application. Each Pharmacy requires an administrator. The constraints are like so: public class Pharmacy implements Serializable { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private int id; @NotNull private String name; @NotNull private String city; @NotNull private String streetAdress; @OneToOne private Stock stock; @NotNull @OneToOne private Administrator administrator; //... Notice how there's a not null constraint in the Administrator field.

问题 On a dataset is a EnforceConstraints property indicating whether the constraints should be enabled. Althought a datatable also can have constraints i cannot disable the constraints for a datatable. My case is that I have datatable which i use in memory with a uniqueconstraint on one of the columns. Sometimes i want to temporarily disable the unique constraint. How can I do this? The only thing I came up with is removing and re-adding the constraint. Is there a better way? 回答1: There is no

问题 On a dataset is a EnforceConstraints property indicating whether the constraints should be enabled. Althought a datatable also can have constraints i cannot disable the constraints for a datatable. My case is that I have datatable which i use in memory with a uniqueconstraint on one of the columns. Sometimes i want to temporarily disable the unique constraint. How can I do this? The only thing I came up with is removing and re-adding the constraint. Is there a better way? 回答1: There is no

问题 I want to ask a few questions about the algorithm in this paper. https://pdfs.semanticscholar.org/9208/65aee7b072c054afa628ba413adda6f3e962.pdf You may wonder why I don't ask the authors directly, actually I have, but unfortunately, I've got no response and I couldn't find direct emails to the authors. You can see the core formula (8) of the algorithm. d(n) = weight value from starting point to current node r(n) = constraint function ɷ = weighted value denoting the impact factor θn = angle