quick SQL Join-like adding columns to a data.table in R -


what i'm trying achieve similar sql 

select * t left join      t2 on t1.key2 = t2.key2      left join t3 on t1.key3 = t3.key3

but in r using data.table. specifically, 'append' two columns t2 , one column t3 first table.
current solution looks like

setkey(t1,key2) t1 <- t2[t1] setkey(t1,key3) t1 <- t3[t1] setkey(t1,key1) # restore original key

this copies entire t1 twice , not quick. on 'inside' t1 quite large dataset ~ 1mln rows , t2 , t3 small 'mapping' tables.
think using j(..) help, i'm new data.tables , can't understand how apply here.
please suggest faster solution join? thanks

since devel version of data.table, v1.9.5 implemented feature of being able join data.tables directly without having set keys using new on argument, can provide quality answer question:

t1[t2, colt2 := i.colt2, on = c(key2="key2")    ][t3, colt3 := i.colt3, on = c(key3="key3")      ][]

it should preserve original key on t1.


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