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Constraints

A constraint is a rule the database enforces on a table's rows: a primary key identifies each row uniquely, a unique constraint prevents duplicates, a foreign key keeps a reference pointing at an existing row in another table, and a check constraint validates values against an expression. The Constraint API adds, inspects and drops these on Centia.io tables without writing DDL, and constraints can also be declared inline when the table is created. A primary key matters in particular for the Feature API and WFS-T editing, which address rows by their key.

Data types are a way to limit the kind of data that can be stored in a table. For many applications, however, the constraint they provide is too coarse. For example, a column containing a product price should probably only accept positive values. But there is no standard data type that accepts only positive numbers. Another issue is that you might want to constrain column data with respect to other columns or rows. For example, in a table containing product information, there should be only one row for each product number.

Add constraint​

A constraint can be of either type primary|unique|foreign|check.

Add constraint in the Centia Web App

Get constraint​

You can either get a single constraint or a collection of constraints.

All constraints for a table
GET https://api.centia.io/api/v4/schemas/rockhall/tables/inductees/constraints HTTP/1.1
Accept: application/json; charset=utf-8
Authorization: Bearer abc123
Specific constraints by name
GET https://api.centia.io/api/v4/schemas/rockhall/tables/inductees/constraints/inductees-id-primary  HTTP/1.1
Accept: application/json; charset=utf-8
Authorization: Bearer abc123

An index object looks like this.

{
  "name": "inductees-id-primary",
  "constraint": "unique",
  "columns": ["id"]
}

Delete constraint​

Delete constraint by name
DELETE https://api.centia.io/api/v4/schemas/rockhall/tables/inductees/constraints/inductees-id-primary HTTP/1.1