Postgres 16

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select '2024-01-12'::date 
       + interval ((8 - extract(isodow from date_trunc('year', now())::text || ' day') 
       as "FirstMondayDate___GivesError_1" 
-- SQL Error [42601]: ERROR: syntax error at or near "("

ERROR:  syntax error at or near "("
LINE 2:        + interval ((8 - extract(isodow from date_trunc('year...
                           ^


select '2024-01-12'::date 
       + ((8 - extract(isodow from date_trunc('year', now())))::text||' day')::interval
       as "FirstMondayDate___GivesError_1 - fixed" 
-- SQL Error [42601]: ERROR: syntax error at or near "("


FirstMondayDate___GivesError_1 - fixed


2024-01-19 00:00:00



SELECT 1


select '2024-01-12'::date 
       + interval (''||(8 - extract(isodow from date_trunc('year', now())))::text||' day')
       as "FirstMondayDate___GivesError_2"
-- SQL Error [42601]: ERROR: syntax error at or near "-"

ERROR:  syntax error at or near "''"
LINE 2:        + interval (''||(8 - extract(isodow from date_trunc('...
                           ^


select '2024-01-12'::date 
      + interval '8 day' 
      - interval extract(isodow from date_trunc('year', now())::text || ' day' 
      as "FirstMondayDate___GivesError_3" 
      -- SQL Error [42601]: ERROR: syntax error at or near "("

ERROR:  syntax error at or near "("
LINE 3:       - interval extract(isodow from date_trunc('year', now(...
                                ^


select '2024-01-12'::date 
     + interval '8 day' 
     - interval (extract(isodow from date_trunc('year', now())) 
     as "FirstMondayDate___GivesError_4" 
  -- SQL Error [42601]: ERROR: syntax error at or near "extract"

ERROR:  syntax error at or near "extract"
LINE 3:      - interval (extract(isodow from date_trunc('year', now(...
                         ^


select '2024-01-12'::date 
     + interval '8 day' 
     - interval ''||(extract(isodow from date_trunc('year', now())))::text||' days'
     as "FirstMondayDate___GivesError_4" 
  -- SQL Error [42601]: ERROR: syntax error at or near "extract"

ERROR:  invalid input syntax for type interval: ""
LINE 3:      - interval ''||(extract(isodow from date_trunc('year', ...
                        ^


select "interval"((extract(isodow from date_trunc('year', now())))::text||' days');


interval


1 day



SELECT 1