select from when sql code example

Example 1: 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);

Example 2: sql select syntax

select [all/distinct] <COL1>, <COL2>, <COL3>
from <TABLE_NAME>
[join <JOIN_CONDITION>]
[where <CONDITION>]
[group by <COLUMN_NAME>]
[having <SEARCH_CONDITION>]
[order by <SORT_SPECIFICATION>]


/*
Specifically for SQL -> Oracle

LEGEND: 
[...]   :   optional entries
<...>   :   your specific entry
*/

Example 3: how select from db

SELECT columname FROM tablename

Example 4: 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