Answers for "select * from query in sql"

return columns from table sql

SELECT *
FROM INFORMATION_SCHEMA.COLUMNS -- INFORMATION_SCHEMA is an ANSI-standard (American National Standard Institute) set of read-only views which provide information about all of the tables, views, columns, and procedures in a database
WHERE TABLE_NAME = N'Customers' -- "N" defines the subsequent string (the string after the N) as being in unicode

sql select from select

SELECT t1.*
FROM   t1
WHERE  t1.MY_FIELD = (SELECT  t2.MY_FIELD
                   FROM    t2
                   WHERE   t2.MY_FIELD = t1.MY_FIELD);

select in select sql

SELECT column1 = (SELECT column-name FROM table-name WHERE condition),       column-names  FROM table-name WEHRE condition