Concatenate,Left Join, Left Keep

[#1]

Hi all,

Can i know the main difference between Concatenate, Left Join, Left Keep.

Please can anyone share your knowledge with some examples.

That will be more easy to understand.

Regards

Venkat

[gandalfgray]

Concatenation

tab1:

Load col_a, col_b, col_c from ...;

Concatenate (tab1)

Load col_b, col_x, col_y from ...;

Concatenation adds the records from the load to a previously loaded table (tab1) in the example.

There will be one table (named tab1 in the example) containing all fields from the "original" tab1, and any new fields from the second load,

so assuming two records was in the original tab1, and three new comes fro the second load:

original tab1

col_a	col_b	col_c
jhkjhkhkj	jjkjjk	green
hhih89hyoh	bhbb	red

second load

col_c	col_x	col_y
black	kjlkjlj	vjvjh
white	bbkbb	bblii
red	dfyyf	vbkh

the concatenated tab1 will look like:

tab1

col_a	col_b	col_c	col_x	col_y
jhkjhkhkj	jjkjjk	green
hhih89hyoh	bhbb	red
		black	kjlkjlj	vjvjh
		white	bbkbb	bblii
		red	dfyyf	vbkh

Left Join

tab1:

Load col_a, col_b, col_c from ...;

Left Join (tab1)

Load col_b, col_x, col_y from ...;

A join adds the fields from the load to a previously loaded table.

If prefixed with Left  (Left Join)  the resulting table only contains combination with a full data set from the first table.

In this case the result will be

tab1

col_a	col_b	col_c	col_x	col_y
jhkjhkhkj	jjkjjk	green
hhih89hyoh	bhbb	red	dfyyf	vbkh

Left Keep

tab1:

Load col_a, col_b, col_c from ...;

tab2:

Left Keep (tab1)

Load col_b, col_x, col_y from ...;

A keep reduces one or both of the involved tables depending on the prefix left/right/inner.

(Both tables are kept, so there will be no concatenation or join)

If prefixed with Left  (Left Keep)  the second table only contains combination with connection to the data set from the first table.

In this case the result will be:

tab1

col_a	col_b	col_c
jhkjhkhkj	jjkjjk	green
hhih89hyoh	bhbb	red

tab2

col_c	col_x	col_y
red	dfyyf	vbkh

[#3]

Thanks GandalfGray.

It is very helpful post.

Thanks once again.

Regards

Venkat

[prasad_dumbre]

Thanks, It cleared my doubt . . . 

[Anonymous]

Excellent but i believe must be:

tab1:

Load col_a, col_b, col_c from ...;

Left Join (tab1)

Load col_c, col_x, col_y from ...;

is col_c and not col_b

thanks

[rohan_mulay]

Consider an example:

Test1:

LOAD * INLINE [

    ID,Salary,l1,l2

    a,1,1,1

    b,2,3,3

    c,1,2,2

];

Test2:

Left keep (Test1)

Load * Inline [

      ID,F3

      a,2

      a,3

      a,4

      b,1

      ];

Refer the screen shot. Check the explanation in the screen shot below.

Please refer the application for above example and check the result by using left join and left keep.

[ghilenasma]

Bonjour 

j'ai un modèle en étoile ou j'ai 2 table qui ont le même article je veux avoir les reste des article art2 et art3 comme l'image suivante 

est se que ça peux fonctionner  avec le keep left   !!  j'ai essayé mais pas de résultat

je serai reconnaissante