addColumn
Syntax
addColumn(table, colNames, colTypes)
Arguments
table can be an in-memory table, a stream table, a DFS table, or a dimension table.
colNames is a string scalar/vector indicating the name(s) of the column(s) to be added.
colTypes is a scalar/vector indicating the data type(s) of the column(s) to be added.
Details
Add a column or columns to a table. It is the only way to add a column to a stream table, a DFS table, or a dimension table. SQL update statement is not supported for these cases.
Please note that the new column should be updated by function loadTable after adding a new column into the distributed table or dimension table by using the command addColumn.
Examples
Example 1: Add columns to a DFS table.
$ ID=1..6
$ x=1..6\5
$ t1=table(ID, x)
$ db=database("dfs://rangedb",RANGE, 1 4 7)
$ pt = db.createPartitionedTable(t1, `pt, `ID)
$ pt.append!(t1);
$ addColumn(pt,["price", "qty"],[DOUBLE, INT]);
After using addColumn
and before data with the new schema is inserted, we can still insert data with the old schema.
$ t2=table(1 as ID, 1.2 as x)
$ pt.append!(t2)
$ select * from pt;
ID |
x |
price |
qty |
---|---|---|---|
1 |
0.2 |
||
2 |
0.4 |
||
3 |
0.6 |
||
1 |
1.2 |
||
4 |
0.8 |
||
5 |
1 |
||
6 |
1.2 |
After data with the new schema is inserted, however, data with the old schema can no longer be inserted.
$ t3=table(1 as ID, 1.6 as x, 10.0 as price, 6 as qty)
$ pt.append!(t3)
$ select * from pt;
ID |
x |
price |
qty |
---|---|---|---|
1 |
0.2 |
||
2 |
0.4 |
||
3 |
0.6 |
||
1 |
1.2 |
||
1 |
1.6 |
10 |
6 |
4 |
0.8 |
||
5 |
1 |
||
6 |
1.2 |
$ t4=table(2 as ID, 2.2 as x)
$ pt.append!(t4);
The data to append contains fewer columns than the schema.
Example 2: Add columns to a stream table.
$ n=10
$ ticker = rand(`MSFT`GOOG`FB`ORCL`IBM,n)
$ x=rand(1.0, n)
$ t=streamTable(ticker, x)
$ share t as st
$ addColumn(st,["price", "qty"],[DOUBLE, INT])
$ insert into st values("MSFT",12.0,25.46,256)
$ select * from st;
ticker |
x |
price |
qty |
---|---|---|---|
MSFT |
0.743241031421349 |
||
FB |
0.254624255700037 |
||
FB |
0.947473830310628 |
||
FB |
0.904140035156161 |
||
MSFT |
0.193251194199547 |
||
MSFT |
0.416090324753895 |
||
MSFT |
0.479371337918565 |
||
ORCL |
0.69910929678008 |
||
GOOG |
0.131539688445628 |
||
MSFT |
0.472390263108537 |
||
MSFT |
12 |
25.46 |
256 |