Relational Operators

In wvlet, you need to use lower-case keywords for SQL-like operators. The following is a list of relational operators in wvlet for manipulating table-format data (i.e., relation):

Operator	Output
from expr	Rows from the given source table, model, value, or file.
select expr, ...	Rows with the given expressions. select * is allowed here.
select distinct expr,...	Rows with distinct values of the given expressions.
select alias = expr, ...	Rows with the given expressions with aliases.
select expr as alias, ...	Rows with the given expressions with aliases.
select as alias	Add an alias to the query result to reference it from another query.
add expr (as alias)?, ...	Same rows with new columns.
rename column as alias, ...	Same rows with the given columns renamed
exclude column, ...	Same rows except the given columns.
where cond	Rows that satisfy the given condition. where can be used multiple times in the same query like from ... where ... where ...
transform column = expr, ...	Same rows with added or updated columns.
group by column, ...	Grouped rows by the given columns. Grouping keys can be referenced as select _1, _2, ... in the subsequent operator. group by returns _1, _2, ..., arbitrary(col1), arbitrary(col2), ... if there is no subsequent agg or select operator.
agg agg_expr, ...	Rows with the grouping keys in group by clause and aggregated values. This is is a shorthand notation for select _1, _2, ..., (agg_expr), .... In aggr_expr, dot-notation like _.count, (column).sum can be used for aggregating grouped rows.
order by expr (asc | desc)?, ...	Rows sorted by the given expression. 1-origin column indexes can be used like 1, 2,
limit n	Rows up to the given number
(left | right | cross)? join table on cond	Joined rows with the given condition. cond can be just common column names between joined tables (e.g., using in SQL)
concat ...	Concatenated rows from multiple sources. Same with UNION ALL in SQL
dedup	Rows with duplicated rows removed. Equivalent to select distinct *
(intersect | except) all? ...	Rows with the intersection (difference) of the given sources. By default it uses set semantics. If all is given, bag semantics will be used.
pivot on pivot_column (in (v1, v2, ...) )?	Rows whose column values in the pivot column are expanded as columns.
pivot on pivot_column (group by grouping columns)? agg agg_expr	Pivoted rows with the given grouping columns and aggregated values.
pipe func(args, ...)	Rows processed by the given table function
shift (to left)? column, ...	Same rows with selected column moved to the left
shift to right column, ...	Same rows with selected column moved to the right
sample method? (size rows? | %)	Randomly sampled rows. Sampling method can be reservoir (default), system, or bernoulli
test (test_expr)	Test the query result, which will be evaluated only in the test-run mode.
debug (| (query))+	Same rows (no change), but run a debug query using the subsequent query expression, prefixed with |

Update Statements

Operator	Description
save as table_name	Save the query result as a new table with the given name
save as 'file name'	Save the query result as a file with the given name
append to table_name	Append the query result to the target table. If the target table doesn't exist, it creates a new one.
append to 'file_name'	Append the query result to the target file. It will create a new file if the file doesn't exist.
delete	Delete input rows from the source table.

Relation Inspection Operators

Operator	Output
describe	Return the schema of the input relation (column_name, column_type)

Commands

Operator	Description
execute sql"..."	Execute a raw SQL statement in the context engine