CREATE TABLE field (fieldid NUMBER)
CREATE TABLE paperfield (fieldid NUMBER, paperid NUMBER)
CREATE TABLE journal (journalid NUMBER, journalname VARCHAR2)
CREATE TABLE paperkeyphrase (paperid NUMBER, keyphraseid NUMBER)
CREATE TABLE keyphrase (keyphraseid NUMBER, keyphrasename VARCHAR2)
CREATE TABLE paperdataset (paperid NUMBER, datasetid NUMBER)
CREATE TABLE paper (paperid NUMBER, title VARCHAR2, venueid NUMBER, year NUMBER, numciting NUMBER, numcitedby NUMBER, journalid NUMBER)
CREATE TABLE author (authorid NUMBER, authorname VARCHAR2)
CREATE TABLE cite (citingpaperid NUMBER, citedpaperid NUMBER)
CREATE TABLE writes (paperid NUMBER, authorid NUMBER)
CREATE TABLE dataset (datasetid NUMBER, datasetname VARCHAR2)
CREATE TABLE venue (venueid NUMBER, venuename VARCHAR2)

How many co-authors has Mark Steedman had ?
SELECT DISTINCT COUNT(DISTINCT author.authorid) FROM author, writes WHERE author.authorname <> 'Mark Steedman' AND writes.authorid = author.authorid AND writes.paperid IN (SELECT WRITESalias1.paperid FROM author AS AUTHORalias1, writes AS WRITESalias1 WHERE AUTHORalias1.authorname = 'Mark Steedman' AND WRITESalias1.authorid = AUTHORalias1.authorid)
WITH "_u_0" AS (SELECT "WRITESalias1"."paperid" FROM "author" "AUTHORalias1" JOIN "writes" "WRITESalias1" ON "AUTHORalias1"."authorid" = "WRITESalias1"."authorid" WHERE "AUTHORalias1"."authorname" = 'Mark Steedman' GROUP BY "paperid") SELECT DISTINCT COUNT(DISTINCT "author"."authorid") FROM "author" JOIN "writes" ON "author"."authorid" = "writes"."authorid" LEFT JOIN "_u_0" "_u_0" ON "_u_0"."" = "writes"."paperid" WHERE "author"."authorname" <> 'Mark Steedman' AND NOT "_u_0"."" IS NULL