On Wednesday, February 27, 2019, Andy Fan <zhihui.fan1...@gmail.com> wrote:
> > The following way works with 2 commands: > > zhifan=# create table t1 (a jsonb); > CREATE TABLE > zhifan=# create unique index t1_a_name on t1 ((a->'name')); > CREATE INDEX > > but know I want to merge them into 1 command, is it possible? > > zhifan=# create table t2 (a jsonb, constraint uk_t2_a_name > unique((a->'name'))); > ERROR: syntax error at or near "(" > LINE 1: ...table t2 (a jsonb, constraint uk_t2_a_name unique((a->'name'... > Not according to the documentation. Unique table constraints can only reference columns in the table as a whole. An expression index must be created separately from the table to which it is attached. Or add a trigger to the table, populate an actual second column (making it unique), and add a table check constraint that that column and the expression are equal. I suspect you’ll be happier having the PK as actual column data anyway. David J.