constraints – Page 9

How can I set aspect ratio constraints programmatically in iOS?

January 6, 2023 by Tarik

Layout Anchors is the most convenient way to set constraints programmatically. Say you want to set 5:1 aspect ratio for your button then you should use: button.heightAnchor.constraint(equalTo: button.widthAnchor, multiplier: 1.0/5.0).isActive = true Here’s the full code: class ViewController: UIViewController { override func viewDidLoad() { super.viewDidLoad() let button = UIButton(type: .custom) button.setTitle(“Login”, for: .normal) button.backgroundColor = … Read more

Declaring a default constraint when creating a table

January 3, 2023 by Tarik

Do it inline with the column creation: [load_date] SMALLDATETIME NOT NULL CONSTRAINT [df_load_date] DEFAULT GETDATE() I have used square brackets rather than quotes as many readers won’t work with QUOTED_IDENTIFIERS on by default.

Rename a constraint in SQL Server?

January 1, 2023 by Tarik

After some more digging, I found that it actually has to be in this form: EXEC sp_rename N’schema.MyIOldConstraint’, N’MyNewConstraint’, N’OBJECT’ Source

List of Constraints from MySQL Database

December 31, 2022 by Tarik

Use the information_schema.table_constraints table to get the names of the constraints defined on each table: select * from information_schema.table_constraints where constraint_schema=”YOUR_DB” Use the information_schema.key_column_usage table to get the fields in each one of those constraints: select * from information_schema.key_column_usage where constraint_schema=”YOUR_DB” If instead you are talking about foreign key constraints, use information_schema.referential_constraints: select * from … Read more

How to create a unique index on a NULL column?

December 31, 2022 by Tarik

Using SQL Server 2008, you can create a filtered index. CREATE UNIQUE INDEX AK_MyTable_Column1 ON MyTable (Column1) WHERE Column1 IS NOT NULL Another option is a trigger to check uniqueness, but this could affect performance.

Get table name by constraint name [duplicate]

December 31, 2022 by Tarik

SELECT owner, table_name FROM dba_constraints WHERE constraint_name = <<your constraint name>> will give you the name of the table. If you don’t have access to the DBA_CONSTRAINTS view, ALL_CONSTRAINTS or USER_CONSTRAINTS should work as well.

Remove all constraints affecting a UIView

December 31, 2022 by Tarik

This approach worked for me: @interface UIView (RemoveConstraints) – (void)removeAllConstraints; @end @implementation UIView (RemoveConstraints) – (void)removeAllConstraints { UIView *superview = self.superview; while (superview != nil) { for (NSLayoutConstraint *c in superview.constraints) { if (c.firstItem == self || c.secondItem == self) { [superview removeConstraint:c]; } } superview = superview.superview; } [self removeConstraints:self.constraints]; self.translatesAutoresizingMaskIntoConstraints = YES; } … Read more

PostgreSQL: default constraint names

December 28, 2022 by Tarik

The standard names for indexes in PostgreSQL are: {tablename}_{columnname(s)}_{suffix} where the suffix is one of the following: pkey for a Primary Key constraint key for a Unique constraint excl for an Exclusion constraint idx for any other kind of index fkey for a Foreign key check for a Check constraint Standard suffix for sequences is … Read more

Postgres: Add constraint if it doesn’t already exist

December 25, 2022 by Tarik

A possible solution is to simply use DROP IF EXISTS before creating the new constraint. ALTER TABLE foo DROP CONSTRAINT IF EXISTS bar; ALTER TABLE foo ADD CONSTRAINT bar …; Seems easier than trying to query information_schema or catalogs, but might be slow on huge tables since it always recreates the constraint. Edit 2015-07-13: Kev … Read more

Constraint name update in PostgreSQL

December 17, 2022 by Tarik

To rename an existing constraint in PostgreSQL 9.2 or newer, you can use ALTER TABLE: ALTER TABLE name RENAME CONSTRAINT constraint_name TO new_constraint_name;