DB2

List all the tables in a database (Excluding system-defined tables)
In DB2, system-defined tables are created in schemas that start with 'SYS'.

SELECT  TABSCHEMA, TABNAME, TYPE, COLCOUNT,KEYCOLUMNS, KEYINDEXID, KEYUNIQUE 
FROM  SYSCAT.TABLES 
WHERE  TABSCHEMA NOT LIKE 'SYS%' AND TYPE = 'T'

db2 list tables

List all the columns in a given table

SELECT  TABSCHEMA, TABNAME, COLNO, COLNAME,TYPENAME, LENGTH, DEFAULT, IDENTITY, HIDDEN
FROM  SYSCAT.COLUMNS 
WHERE  TABSCHEMA NOT LIKE 'SYS%' AND TABNAME = 'TABLE_NAME' 

List all the indexes available for a given table

SELECT  INDNAME, DEFINER, TABSCHEMA, TABNAME, COLNAMES, COLCOUNT, UNIQUERULE, INDEXTYPE 
FROM  SYSCAT.INDEXES
WHERE  TABSCHEMA NOT LIKE 'SYS%' AND TABNAME = 'TABLE_NAME'

list all types

select typename from syscat.datatypes

db2 date and timestamp
The default format used for dates is determined by the territory code of the database. Let's say the default format is 'yyyy-mm-dd'.

DATE('2008-01-30')
TIMESTAMP('2007-11-30-00.00.00')

For more detail, you can refer to this article.