Results of 1 - 10 of about 16 for expr (0.006 sec.)
- Window Functions 14971
- DuckDB supports window functions , which can use multiple rows to calculate a value for each row. Window functions are blocking operators , i.e., they require their entire input to be buffered, making them one of the most memory-intensive o
...row) / total partition rows. dense_rank() The rank of the current row without gaps; this function counts peer groups. fill(expr [ ORDER BY ordering]) Fill in missing values using linear interpolation with ORDER BY as the X-axis. first_value(expr[ ORD...ER BY ordering][ IGNORE NULLS]) Returns expr evaluated at the row that is the first row (with a non-null value of expr if IGNORE NULLS is set) of the window frame. lag...(expr[, offset[, default]][ ORDER BY ordering][ IGNORE NULLS]) Returns expr evaluated at the row that is offset rows (among rows... - https://man.mtool.work/duckdb/2.0/sql/functions/window_functions.html
- Expression API 9374
- The Expression class represents an instance of an expression . Why Would I Use the Expression API? Use expressions to build filters and computed columns in Python. They are useful when column names or conditions depend on your code. import
...rice_column = "price" rel = duckdb.from_df(sales) print(rel.filter(col(price_column) > 30).fetchall()) [('hammer', 42)] An expression is passed to a method of a relation , such as select , filter , aggregate or sort . str() of an expression returns i...in parentheses: print((col("a") > 1) & col("b")) (("a" > 1) AND "b") The duckdb module has a short helper for each kind of expression, and this page uses them throughout. The constructors of the earlier expression API still work and build the same ex...pressions, but new code should use the helpers: Helper Older constructor col(name) ColumnExpression(name) lit(value) ConstantExpression(value) when(condition).then(value) CaseExpression(condition, value) fn(name, *ar... - https://man.mtool.work/duckdb/2.0/clients/python/expression.html
- Relational API 9374
- The Relational API builds a query one step at a time from Python. A relation, a DuckDBPyRelation , is a piece of SQL text: the methods of the Transformation and Functions sections return a new relation whose text extends the one they were c
...f one row, several tuples for several rows or the values of one row as separate arguments. A value is a Python value or an Expression. Example import duckdb duckdb_conn = duckdb.connect() rel = duckdb_conn.values([1, 'a']) rel.show() Result ┌───────┬...n the view named virtual_table_name that refers to the relation object. The name is this query's own: it is a common table expression over the relation, and a catalog entry for the length of the call, so a table function or a query that defines the n...inst it. Nothing of it is left afterwards. A statement that does not only read, which includes a SELECT whose common table expression writes, runs at the call and the relation holds what it returned. Parameters virtual_table_name : str The name under... - https://man.mtool.work/duckdb/2.0/clients/python/relational_api.html
- Python Client API 9322
- Connection class duckdb. Appender Bases: object append_row ( self , * args ) → None Buffer one row, one value per column, each converted as an executemany parameter would be append_rows ( self , rows : object ) → None Buffer each row of an
...hod reads its rows, and runs again on every read. Detailed examples can be found at Relational API page . aggregate ( aggr_expr : object , group_expr : object = '' ) → DuckDBPyRelation Compute the aggregate aggr_expr by the optional groups group_expr...al API page . alias Get the name of the current alias. Detailed examples can be found at Relational API page . any_value ( expression : str , groups : str = '' , window_spec : str = '' , projected_columns : str = '' ) → DuckDBPyRelation Returns the f...irst non-null value from a given expression. Detailed examples can be found at Relational API page . apply ( function_name : str , function_aggr : str , group_e... - https://man.mtool.work/duckdb/2.0/clients/python/reference/
- Casting 8421
- Casting refers to the operation of converting a value in a particular data type to the corresponding value in another data type. Casting can occur either implicitly or explicitly. The syntax described here performs an explicit cast. More in
...on on casting can be found on the typecasting page . Explicit Casting The standard SQL syntax for explicit casting is CAST(expr AS TYPENAME) , where TYPENAME is a name (or alias) of one of DuckDB's data types . DuckDB also supports the shorthand expr...TRY_CAST('hello' AS INTEGER) AS i; i NULL cast_to_type Function The cast_to_type function allows generating a cast from an expression to the type of another column. For example: SELECT cast_to_type('42', NULL::INTEGER) AS result; ┌───────┐ │ res │ │... - https://man.mtool.work/duckdb/2.0/sql/expressions/cast.html
- List Type 8300
- A LIST column encodes lists of values. Fields in the column can have values with different lengths, but they must all have the same underlying type. LIST s are typically used to store arrays of numbers, but can contain any uniform data type
...pes. For storing fixed-length lists, DuckDB uses the ARRAY type . Creating Lists Lists can be created using the list_value(expr, ...) function or the equivalent bracket notation [expr, ...] . The expressions can be constants or arbitrary expressions....n and Ordering The LIST type can be compared using all the comparison operators . These comparisons can be used in logical expressions such as WHERE and HAVING clauses, and return BOOLEAN values . The LIST ordering is defined positionally using the f... - https://man.mtool.work/duckdb/2.0/sql/data_types/list.html
- Struct Data Type 8196
- Conceptually, a STRUCT column contains an ordered list of columns called “entries”. The entries are referenced by name using strings. This document refers to those entry names as keys. Each row in the STRUCT column must have the same keys.
...ness. Structs with unnamed entries are represented by the TUPLE type , which can be created using the row function or the (expr, ...) notation. See an example below and the STRUCT functions documentation for details. See the data types overview for a...comparison between nested data types. Creating Structs Structs can be created using the struct_pack(name := expr, ...) function, the equivalent array notation {'name': expr, ...} , or using a row variable. To create a struct with unnam...also be used. Note that this uses single quotes ( ' ) since the goal is to specify a certain string key and only constant expressions may be used inside the brackets (no expressions): SELECT a['x space'] FROM (SELECT {'x space': 1, 'y': 2, 'z': 3} A... - https://man.mtool.work/duckdb/2.0/sql/data_types/struct.html
- Utility Functions 8196
- Scalar Utility Functions The functions below are difficult to categorize into specific function types and are broadly useful. Name Description alias(column) Return the name of the column. can_cast_implicitly(source_value, target_value) Whet
...value. checkpoint(database) Synchronize WAL with file for (optional) database without interrupting transactions. coalesce(expr, ...) Return the first expression that evaluates to a non- NULL value. Accepts 1 or more parameters. Each expression can b...bb5e-222f4e14b687 . get_block_size(database) Returns the block size of the attached database with the given name. get_type(expression) Returns the data type of the result of the expression as a value of type TYPE . getenv(var) Returns the value of th...arameter is optional. Only available when the ICU extension is installed. if(a, b, c) Ternary conditional operator. ifnull(expr, other) A two-argument version of coalesce. in_search_path(database_name, schema_name) Returns whether or not the given da... - https://man.mtool.work/duckdb/2.0/sql/functions/utility.html
- CASE Expression 7919
- The CASE expression performs a switch based on a condition. The basic form is identical to the ternary condition used in many programming languages ( CASE WHEN cond THEN a ELSE b END is equivalent to cond ? a : b ). With a single condition
...this can be expressed with IF(cond, a, b) . CREATE OR REPLACE TABLE integers AS SELECT unnest([1, 2, 3]) AS i; SELECT i, CASE WHEN i > 2 TH...OM integers; i test 1 0 2 0 3 1 This is equivalent to: SELECT i, IF(i > 2, 1, 0) AS test FROM integers; The WHEN cond THEN expr part of the CASE expression can be chained, whenever any of the conditions returns true for a single tuple, the correspond...ing expression is evaluated and returned. CREATE OR REPLACE TABLE integers AS SELECT unnest([1, 2, 3]) AS i; SELECT i, CASE WHEN i... - https://man.mtool.work/duckdb/2.0/sql/expressions/case.html
- Array Type 7867
- An ARRAY column stores fixed-sized arrays. All fields in the column must have the same length and the same underlying type. Arrays are typically used to store arrays of numbers, but can contain any uniform data type, including ARRAY , LIST
...s variable-length fields. DuckDB's ARRAY type is fixed-length. Creating Arrays Arrays can be created using the array_value(expr, ...) function . Construct with the array_value function: SELECT array_value(1, 2, 3); You can always implicitly cast an a... - https://man.mtool.work/duckdb/2.0/sql/data_types/array.html
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