update!

update!(table, colNames, newValues, [filter])

table is a DolphinDB table. It can be a partitioned in-memory table.

colNames is a string scalar/vector indicating the columns to be updated.

newValues is a piece of metacode with the operations for the specified columns. Metacode is objects or expressions within "<" and ">". For details about metacode, please refer to Metaprogramming.

filter (optional) is a piece of metacode with filterting conditions.

Update columns of a table in place. If a column in colNames doesn't exist, create a new column; otherwise update the existing column. If a filter is specified, only rows satisfying the filtering condition will be updated.

This operation is parallel if the table is a partitioned table and if the parallel processing feature is enabled (when the configuration parameter localExcutors > 0).

n=20000000
workDir = "C:/DolphinDB/Data"
if(!exists(workDir)) mkdir(workDir)
trades=table(rand(`IBM`MSFT`GM`C`YHOO`GOOG,n) as sym, 2000.01.01+rand(365,n) as date, 10.0+rand(2.0,n) as price, rand(1000,n) as qty)
trades.saveText(workDir + "/trades.txt");

trades = ploadText(workDir + "/trades.txt")
select top 10 * from trades;

trades.update!(`qty, <qty+10>)
select top 10 * from trades;

trades.update!(`qty`price, <[qty*2, price/2]>)
select top 10 * from trades;

trades.update!(`qty`price, <[qty*2, price/2]>, <(sym in `IBM`MSFT`GM`GOOG) and date>=2000.07.01>)
select top 10 * from trades;