Table creation
In this task, the goal is to create a table to exemplify most commonly used data types and options.
You are encouraged to solve this task according to the task description, using any language you may know.
PostgreSQL
Postgres developers, please feel free to add additional data-types you commonly use to this example.
-- This is a comment CREATE SEQUENCE account_seq start 100; CREATE TABLE account ( account_id int4 PRIMARY KEY DEFAULT nextval('account_seq'), created date not null default now(), active bool not null default 't', username varchar(16) unique not null, balance float default 0, age int2, notes text ); CREATE TABLE account_note ( account_id int4 not null REFERENCES account, created timestamp not null default now(), note text not null, unique(account_id, note) ); -- bool: 't', 'f' or NULL -- int2: -32768 to +32767 -- int4: -2147483648 to +2147483647 -- float: decimal -- date: obvious -- timestamp: date time -- char(#): space padded text field with length of # -- varchar(#): variable length text field up to # -- text: not limited
Python
The sqlite3 database is a part of the Python standard library. It does not associate type with table columns, any cell can be of any type. <lang python>>>> import sqlite3 >>> conn = sqlite3.connect(':memory:') >>> c = conn.cursor() >>> c.execute(create table stocks (date text, trans text, symbol text,
qty real, price real))
<sqlite3.Cursor object at 0x013263B0> >>> # Insert a row of data c.execute("""insert into stocks
values ('2006-01-05','BUY','RHAT',100,35.14)""")
<sqlite3.Cursor object at 0x013263B0> >>> for t in [('2006-03-28', 'BUY', 'IBM', 1000, 45.00),
('2006-04-05', 'BUY', 'MSOFT', 1000, 72.00), ('2006-04-06', 'SELL', 'IBM', 500, 53.00), ]:
c.execute('insert into stocks values (?,?,?,?,?)', t)
<sqlite3.Cursor object at 0x013263B0>
<sqlite3.Cursor object at 0x013263B0>
<sqlite3.Cursor object at 0x013263B0>
>>> # Data retrieval
>>> c = conn.cursor()
>>> c.execute('select * from stocks order by price')
<sqlite3.Cursor object at 0x01326530>
>>> for row in c:
print row
(u'2006-01-05', u'BUY', u'RHAT', 100.0, 35.140000000000001)
(u'2006-03-28', u'BUY', u'IBM', 1000.0, 45.0)
(u'2006-04-06', u'SELL', u'IBM', 500.0, 53.0)
(u'2006-04-05', u'BUY', u'MSOFT', 1000.0, 72.0)
>>> </lang>
Tcl
Tables, as used in relational databases, seem far away conceptually from Tcl. However, the following code demonstrates how a table (implemented as a list of lists, the first being the header line) can be type-checked and rendered: <lang Tcl>proc table_update {_tbl row args} {
upvar $_tbl tbl set heads [lindex $tbl 0] if {$row eq "end+1"} { lappend tbl [lrepeat [llength $heads] {}] set row [expr [llength $tbl]-1] } foreach {key val} $args { set col [lsearch $heads $key*] foreach {name type} [split [lindex $heads $col] |] break if {$type eq "float"} {set type double} if {$type eq "date"} { if [catch {clock scan $val}] { error "bad date value $val" } } elseif {$type ne ""} { if ![string is $type -strict $val] { error "bad $type value $val" } } lset tbl $row $col $val }
} proc table_format table {
set maxs {} foreach item [lindex $table 0] { set item [lindex [split $item |] 0] lappend maxs [string length $item] } foreach row [lrange $table 1 end] { set i 0 foreach item $row max $maxs { if {[string length $item]>$max} {lset maxs $i [string length $item]} incr i } } set head + foreach max $maxs {append head -[string repeat - $max]-+} set res $head\n foreach row $table { if {$row eq [lindex $table 0]} { regsub -all {\|[^ ]+} $row "" row } append res | foreach item $row max $maxs { append res [format " %-${max}s |" $item] } append res \n if {$row eq [lindex $table 0]} { append res $head \n } } append res $head
}
- ------------------------------------- Test and demo:
set mytbl [list [list \
account_id|int \ created|date \ active|bool \ username \ balance|float \ ]]
table_update mytbl end+1 \
account_id 12345 \ username "John Doe" \ balance 0.0 \ created 2009-05-13
table_update mytbl end+1 \
account_id 12346 \ username "Jane Miller" \ balance 0.0 \ created 2009-05-14
puts [table_format $mytbl]</lang> Output:
+------------+------------+--------+-------------+---------+ | account_id | created | active | username | balance | +------------+------------+--------+-------------+---------+ | 12345 | 2009-05-13 | | John Doe | 0.0 | | 12346 | 2009-05-14 | | Jane Miller | 0.0 | +------------+------------+--------+-------------+---------+