POSTGRES Group by / Inner Join - sql

Question

I am having problems writing a query to summarize the number trips from a OD matrix table. I am still new to using databases other than MS Access, so please forgive my inexperience. SMGZ is the table with the number of zones and matrix_od is the matrix table with all the OD pairs(4109*4109) from zone to zone with the total number of trip types. I am not sure this is the best way to write this query. SO what i need to do is summarize 4 types of trips(LHDT,MHDT,HHDT,HDT_Tota) by the OD. Help is much appreciated.
SELECT
smgz.smg_zone AS "O_ID",
smgz.x AS "O_X",
smgz.y AS "O_Y",
smgz1.smg_zone AS "D_ID",
smgz1.x AS "D_X",
smgz1.y AS "D_Y",
SUM(matrix_od."LHDT") AS "LHDT_Tot",
SUM(matrix_od."MHDT") AS "MHDT_Tot",
SUM(matrix_od."HHDT") AS "HHDT_Tot",
SUM(matrix_od."TOT_HDT") AS "HDT_Tot"
FROM
public.smgz,
public.matrix_od,
public.smgz smgz1
GROUP BY
"O_ID","O_X","O_Y","D_ID","D_X","D_Y"
INNER JOIN
smgz on matrix_od.O_ID = smgz.ID
INNER JOIN
smgz1 on matrix_od.D_ID = smgz1.ID;
ERROR: syntax error at or near "INNER"
LINE 18: INNER JOIN
^
********** Error **********
ERROR: syntax error at or near "INNER"
SQL state: 42601
Character: 414

Answer 1

As stated in comments the two main errors are that the group by clause is in the wrong place, it should be after the joins, and that you are mixing implicit joins (multiple tables in the from clause) with explicit joins (using the join keyword). The fix is to change this part:
FROM
public.smgz,
public.matrix_od,
public.smgz smgz1
GROUP BY
"O_ID","O_X","O_Y","D_ID","D_X","D_Y"
INNER JOIN
smgz on matrix_od.O_ID = smgz.ID
INNER JOIN
smgz1 on matrix_od.D_ID = smgz1.ID;
to this:
FROM
public.matrix_od
INNER JOIN
public.smgz on matrix_od.O_ID = smgz.ID
INNER JOIN
public.smgz smgz1 on matrix_od.D_ID = smgz1.ID
GROUP BY
"O_ID","O_X","O_Y","D_ID","D_X","D_Y";

Answer 2

That did the trick! Thank you #a_horse_with_no_name & #Lamak.
SELECT
smgz.smg_zone AS "O_ID",
smgz.x AS "O_X",
smgz.y AS "O_Y",
smgz1.smg_zone AS "O_ID",
smgz1.x AS "D_X",
smgz1.y AS "D_Y",
SUM(matrix_od."LHDT") AS "LHDT_Tot",
SUM(matrix_od."MHDT") AS "MHDT_Tot",
SUM(matrix_od."HHDT") AS "HHDT_Tot",
SUM(matrix_od."TOT_HDT") AS "HDT_Tot"
FROM
public.matrix_od
INNER JOIN
smgz on matrix_od."O_ID" = smgz."id"
INNER JOIN
public.smgz smgz1 on matrix_od."D_ID" = smgz1."id"
GROUP BY
smgz.smg_zone,smgz.x,smgz.y,smgz1.smg_zone,smgz1.x,smgz1.y;