--         File: queens_4_solution_pg.sql
--      Version: 1.2
-- Last Changed: 2017-01-02
--           by: Damir;  https://www.damirsystems.com
--      Project: Eight Queens
--  Description: Part 4; Solution
--           DB: PostgreSQL


CREATE OR REPLACE VIEW solution AS

WITH 
w AS ( -- search space; place by columns

SELECT
      q1.SQUARE as S1
    , q2.SQUARE as S2
    , q3.SQUARE as S3
    , q4.SQUARE as S4
    , q5.SQUARE as S5
    , q6.SQUARE as S6
    , q7.SQUARE as S7
    , q8.SQUARE as S8
FROM board1 as q1

JOIN board1 as q2 ON q2.CL = 'b' 
                 and q2.RW not in (q1.rw)  
                 and q2.RW_NO not BETWEEN (q1.RW_NO - 1)
                                      and (q1.RW_NO + 1)

JOIN board1 as q3 ON q3.CL  = 'c' 
                 and q3.RW not in (q1.RW, q2.rw) 
                 and q3.RW_NO not BETWEEN (q2.RW_NO - 1)
                                      and (q2.RW_NO + 1)

JOIN board1 as q4 ON q4.CL = 'd' 
                 and q4.RW not in (q1.RW, q2.RW, q3.rw)
                 and q4.RW_NO not BETWEEN (q3.RW_NO - 1)
                                      and (q3.RW_NO + 1)

JOIN board1 as q5 ON q5.CL = 'e' 
                 and q5.RW not in (q1.RW, q2.RW, q3.RW, q4.rw)
                 and q5.RW_NO not BETWEEN (q4.RW_NO - 1)
                                      and (q4.RW_NO + 1) 

JOIN board1 as q6 ON q6.CL = 'f' 
                 and q6.RW not in (q1.RW, q2.RW, q3.RW, q4.RW, q5.rw)
                 and q6.RW_NO not BETWEEN (q5.RW_NO - 1)
                                      and (q5.RW_NO + 1) 

JOIN board1 as q7 ON q7.CL = 'g' 
                 and q7.RW not in (q1.RW, q2.RW, q3.RW, q4.RW, q5.RW, q6.rw)
                 and q7.RW_NO not BETWEEN (q6.RW_NO - 1)
                                      and (q6.RW_NO + 1)

JOIN board1 as q8 ON q8.CL = 'h' 
                 and q8.RW not in (q1.RW, q2.RW, q3.RW, q4.RW, q5.RW, q6.RW, q7.rw)
                 and q8.RW_NO not BETWEEN (q7.RW_NO - 1)
                                      and (q7.RW_NO + 1)

WHERE q1.CL = 'a'
)

SELECT S1, S2, S3, S4, S5, S6, S7, S8
FROM w

WHERE not exists ( -- placing queen 2

        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE = w.s1

        INTERSECT

        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE = w.s2  
      )

  and not exists ( -- placing queen 3
        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE in (w.s1, w.s2)

        INTERSECT

        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE = w.s3  
      )

  and not exists ( -- placing queen 4
        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE in (w.s1, w.s2, w.s3)

        INTERSECT

        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE = w.s4  
      )

  and not exists ( -- placing queen 5
        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE in (w.s1, w.s2, w.s3, w.s4)

        INTERSECT

        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE = w.s5
      )

  and not exists ( -- placing queen 6
        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE in (w.s1, w.s2, w.s3, w.s4, w.s5)

        INTERSECT

        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE = w.s6
      )

  and not exists ( -- placing queen 7
        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE in (w.s1, w.s2, w.s3, w.s4, w.s5, w.s6)

        INTERSECT

        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE = w.s7
      )

  and not exists (-- placing queen 8
        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE in (w.s1, w.s2, w.s3, w.s4, w.s5, w.s6, w.s7)

        INTERSECT

        SELECT distinct e.ANCHOR, e.MOV_DIR 
          FROM square_line as e 
         WHERE e.SQUARE = w.s8
      )
;

COMMENT ON VIEW solution IS '
[p_07] Placing queens on squares (S1), (S2), (S3), (S4), (S5), 
(S6), (S7), and (S8) is a solution to the puzzle.

KEY {S1, S2, S3, S4, S5, S6, S7, S8}
';