constraints

问题 I've been struggling with this check constraint for a few hours and was hoping someone would be kind enough to explain why this check constraint isn't doing what I think it should be doing. ALTER TABLE CLIENTS add CONSTRAINT CHK_DISABILITY_INCOME_TYPE_ID CHECK ((IS_DISABLED IS NULL AND DISABILITY_INCOME_TYPE_ID IS NULL) OR (IS_DISABLED = 0 AND DISABILITY_INCOME_TYPE_ID IS NULL) OR (IS_DISABLED = 1)); Essentially, you must be disabled to collect disability income. It appears as though the

问题 I'm looking for the best way to go about adding a constraint to a table that is effectively a unique index on the relationship between the record and the rest of the records in that table. Imagine the following table describing the patrols of various guards (from the previous watchman scenario) PK PatrolID Integer FK GuardID Integer Starts DateTime Ends DateTime We start with a constraint specifying that the start and end times must be logical: Ends >= Starts However I want to add another

问题 I have created an app which is working fine in iphone devices , i have tried auto layout and constraints so that it would work same on iphone devices on the ipad , but the problem is its okay to look in iphone but in ipad devices distance seems too wide . for example if i have set constraints distance which is 8 its okay in iphone devices but its seems to wide in ipad device. also is there a way we can image or buttons or components would resize bigger so that will fit to the ipad? is there a

问题 Can I create a database constraint on a TEXT column in SQLite disallowing the value of the column to be empty string "" ? I want to allow the column to be null , but disallow empty string. 回答1: Yes you can: sqlite> create table foo (bar TEXT, CHECK(bar <> '')); sqlite> insert into foo values (NULL); sqlite> insert into foo values ('bla'); sqlite> insert into foo values (''); Error: constraint failed 回答2: You can use a CHECK constraint (http://www.sqlite.org/lang_createtable.html): SQLite

问题 I commonly have a "oh yeah" moment writing F# when I realize I need an extra value somewhere. This is generally easily done by adding another value to the tuple being passed around. However, this means that various maps/sorts/collects/etc. need updating, and in particular the functions fst/snd only work on tuples of length 2. It's not a huge issue, but it's annoying enough during exploratory development that I though I'd write a helper to alleviate the annoyance: let inline get2 (t:^a) = (^a

问题 Table: Relatives emp_id dep_id (composite primary key) We have to restrict one employee to three dependents. 回答1: This cannot be done using a check constraint alone, but there is a way using a materialized view and a check constraint as I demonstrate here on my blog. For your example this would be: create materialized view emp_dep_mv build immediate refresh complete on commit as select emp_id, count(*) cnt from relatives group by emp_id; alter table emp_dep_mv add constraint emp_dep_mv_chk

问题 I would like to solve the following problem using constraints but i actually don't know where to begin so i decided to post it here for help. *** Fitting squares *** Given the set of black squares of Figure 1 (a 2x2, 3x3, 4x4 and a 5x5 square), fit them all into the white rectangle of Figure 1 (a 7x9 rectangle), and this in such a way that there is no overlap between the squares. Note that the black squares can only be put on integer coordinates. Formulate the problem above as a constraint

问题 Almost all the information I had needed about a database, I could find in information_schema This time I needed to read details of all foreign keys in a database through single query I found every thing in information_schema.key_Column_usage but could not find the constraints like on delete, on update I could do show create table for all individual tables. But is there any way to get these details through some select query like this? SELECT CONSTRAINT_NAME, TABLE_NAME,COLUMN_NAME, REFERENCED

问题 I'm currently using @Entity public class ... { /** * @return the loginName */ @Column(unique=true) public String getLoginName() { return loginName; } but like to have a case-insensitive constraint such that a login name "UPPERCASE" is not allowed when there is already a login name "uppercase" in the database. Is there anything I can use or do I have to create the dirty workaround of storing a lower case version in a separate column? 回答1: This is not something covered by JPA, and I'd say not

问题 This question already has answers here : Can't operator == be applied to generic types in C#? (12 answers) Closed 6 years ago . I have the following code: class Foo<T> where T : struct { private T t; [...] public bool Equals(T t) { return this.t == t; } } When I try to compile, it gives me the following error: Operator '==' cannot be applied to operands of type 'T' and 'T' Why can't it be done? If the constraint was where T : class it would have worked. But I need it to be value type because