Define the base components of SQL expression trees.
All components are derived from a common base class ClauseElement. Common behaviors are organized based on class hierarchies, in some cases via mixins.
All object construction from this package occurs via functions which in some cases will construct composite ClauseElement structures together, and in other cases simply return a single ClauseElement constructed directly. The function interface affords a more "DSL-ish" feel to constructing SQL expressions and also allows future class reorganizations.
Even though classes are not constructed directly from the outside, most classes which have additional public methods are considered to be public (i.e. have no leading underscore). Other classes which are "semi-public" are marked with a single leading underscore; these classes usually have few or no public methods and are less guaranteed to stay the same in future releases.
Return an Alias object.
An Alias represents any FromClause with an alternate name assigned within SQL, typically using the AS clause when generated, e.g. SELECT * FROM table AS aliasname.
Similar functionality is available via the alias() method available on all FromClause subclasses.
- selectable
- any FromClause subclass, such as a table, select statement, etc..
- alias
- string name to be assigned as the alias. If None, a random name will be generated.
Join a list of clauses together using the AND operator.
The & operator is also overloaded on all _CompareMixin subclasses to produce the same result.
Return a BETWEEN predicate clause.
Equivalent of SQL clausetest BETWEEN clauseleft AND clauseright.
The between() method on all _CompareMixin subclasses provides similar functionality.
Create a bind parameter clause with the given key.
Produce a CASE statement.
Return a CAST function.
Equivalent of SQL CAST(clause AS totype).
Use with a TypeEngine subclass, i.e:
cast(table.c.unit_price * table.c.qty, Numeric(10,4))
or:
cast(table.c.timestamp, DATE)
Return a textual column clause, as would be in the columns clause of a SELECT statement.
The object returned is an instance of _ColumnClause, which represents the "syntactical" portion of the schema-level Column object.
- text
- the name of the column. Quoting rules will be applied to the clause like any other column name. For textual column constructs that are not to be quoted, use the literal_column() function.
- type_
- an optional TypeEngine object which will provide result-set translation for this column.
Return an Insert clause element.
Similar functionality is available via the insert() method on Table.
- table
- The table to be inserted into.
- values
- A dictionary which specifies the column specifications of the INSERT, and is optional. If left as None, the column specifications are determined from the bind parameters used during the compile phase of the INSERT statement. If the bind parameters also are None during the compile phase, then the column specifications will be generated from the full list of table columns.
If both values and compile-time bind parameters are present, the compile-time bind parameters override the information specified within values on a per-key basis.
The keys within values can be either Column objects or their string identifiers. Each key may reference one of:
If a SELECT statement is specified which references this INSERT statement's table, the statement will be correlated against the INSERT statement.
Return an INTERSECT ALL of multiple selectables.
The returned object is an instance of CompoundSelect.
Return a JOIN clause element (regular inner join).
The returned object is an instance of Join.
Similar functionality is also available via the join() method on any FromClause.
- left
- The left side of the join.
- right
- The right side of the join.
- onclause
- Optional criterion for the ON clause, is derived from foreign key relationships established between left and right otherwise.
To chain joins together, use the join() or outerjoin() methods on the resulting Join object.
Return a _Label object for the given ColumnElement.
A label changes the name of an element in the columns clause of a SELECT statement, typically via the AS SQL keyword.
This functionality is more conveniently available via the label() method on ColumnElement.
- name
- label name
- obj
- a ColumnElement.
Return a literal clause, bound to a bind parameter.
Literal clauses are created automatically when non- ClauseElement objects (such as strings, ints, dates, etc.) are used in a comparison operation with a _CompareMixin subclass, such as a Column object. Use this function to force the generation of a literal clause, which will be created as a _BindParamClause with a bound value.
- value
- the value to be bound. can be any Python object supported by the underlying DBAPI, or is translatable via the given type argument.
- type_
- an optional TypeEngine which will provide bind-parameter translation for this literal.
Return a textual column clause, as would be in the columns clause of a SELECT statement.
The object returned is an instance of _ColumnClause, which represents the "syntactical" portion of the schema-level Column object.
- text
- the name of the column. Quoting rules will not be applied to the column. For textual column constructs that should be quoted like any other column construct, use the column() function.
- type
- an optional TypeEngine object which will provide result-set translation for this column.
Return a negation of the given clause, i.e. NOT(clause).
The ~ operator is also overloaded on all _CompareMixin subclasses to produce the same result.
Join a list of clauses together using the OR operator.
The | operator is also overloaded on all _CompareMixin subclasses to produce the same result.
Return an OUTER JOIN clause element.
The returned object is an instance of Join.
Similar functionality is also available via the outerjoin() method on any FromClause.
- left
- The left side of the join.
- right
- The right side of the join.
- onclause
- Optional criterion for the ON clause, is derived from foreign key relationships established between left and right otherwise.
To chain joins together, use the join() or outerjoin() methods on the resulting Join object.
create an 'OUT' parameter for usage in functions (stored procedures), for databases whith support them.
The outparam can be used like a regular function parameter. The "output" value will be available from the ResultProxy object via its out_parameters attribute, which returns a dictionary containing the values.
Returns a SELECT clause element.
Similar functionality is also available via the select() method on any FromClause.
The returned object is an instance of Select.
All arguments which accept ClauseElement arguments also accept string arguments, which will be converted as appropriate into either text() or literal_column() constructs.
- columns
A list of ClauseElement objects, typically ColumnElement objects or subclasses, which will form the columns clause of the resulting statement. For all members which are instances of Selectable, the individual ColumnElement members of the Selectable will be added individually to the columns clause. For example, specifying a Table instance will result in all the contained Column objects within to be added to the columns clause.
This argument is not present on the form of select() available on Table.
- whereclause
- A ClauseElement expression which will be used to form the WHERE clause.
- from_obj
- A list of ClauseElement objects which will be added to the FROM clause of the resulting statement. Note that "from" objects are automatically located within the columns and whereclause ClauseElements. Use this parameter to explicitly specify "from" objects which are not automatically locatable. This could include Table objects that aren't otherwise present, or Join objects whose presence will supercede that of the Table objects already located in the other clauses.
- **kwargs
Additional parameters include:
- order_by
- a scalar or list of ClauseElement objects which will comprise the ORDER BY clause of the resulting select.
- group_by
- a list of ClauseElement objects which will comprise the GROUP BY clause of the resulting select.
- having
- a ClauseElement that will comprise the HAVING clause of the resulting select when GROUP BY is used.
- use_labels=False
- when True, the statement will be generated using labels for each column in the columns clause, which qualify each column with its parent table's (or aliases) name so that name conflicts between columns in different tables don't occur. The format of the label is <tablename>_<column>. The "c" collection of the resulting Select object will use these names as well for targeting column members.
- distinct=False
- when True, applies a DISTINCT qualifier to the columns clause of the resulting statement.
- for_update=False
- when True, applies FOR UPDATE to the end of the resulting statement. Certain database dialects also support alternate values for this parameter, for example mysql supports "read" which translates to LOCK IN SHARE MODE, and oracle supports "nowait" which translates to FOR UPDATE NOWAIT.
- bind=None
- an Engine or Connection instance to which the resulting Select object will be bound. The Select object will otherwise automatically bind to whatever Connectable instances can be located within its contained ClauseElement members.
- limit=None
- a numerical value which usually compiles to a LIMIT expression in the resulting select. Databases that don't support LIMIT will attempt to provide similar functionality.
- offset=None
- a numerical value which usually compiles to an OFFSET expression in the resulting select. Databases that don't support OFFSET will attempt to provide similar functionality.
- scalar=False
- deprecated. use select(...).as_scalar() to create a "scalar column" proxy for an existing Select object.
- correlate=True
- indicates that this Select object should have its contained FromClause elements "correlated" to an enclosing Select object. This means that any ClauseElement instance within the "froms" collection of this Select which is also present in the "froms" collection of an enclosing select will not be rendered in the FROM clause of this select statement.
Return a Table object.
This is a primitive version of the Table object, which is a subclass of this object.
Create literal text to be inserted into a query.
When constructing a query from a select(), update(), insert() or delete(), using plain strings for argument values will usually result in text objects being created automatically. Use this function when creating textual clauses outside of other ClauseElement objects, or optionally wherever plain text is to be used.
- text
- The text of the SQL statement to be created. use :<param> to specify bind parameters; they will be compiled to their engine-specific format.
- bind
- An optional connection or engine to be used for this text query.
- bindparams
- A list of bindparam() instances which can be used to define the types and/or initial values for the bind parameters within the textual statement; the keynames of the bindparams must match those within the text of the statement. The types will be used for pre-processing on bind values.
- typemap
- A dictionary mapping the names of columns represented in the SELECT clause of the textual statement to type objects, which will be used to perform post-processing on columns within the result set (for textual statements that produce result sets).
Return a UNION of multiple selectables.
The returned object is an instance of CompoundSelect.
A similar union() method is available on all FromClause subclasses.
Return a UNION ALL of multiple selectables.
The returned object is an instance of CompoundSelect.
A similar union_all() method is available on all FromClause subclasses.
Return an Update clause element.
Similar functionality is available via the update() method on Table.
- table
- The table to be updated.
- whereclause
- A ClauseElement describing the WHERE condition of the UPDATE statement.
- values
- A dictionary which specifies the SET conditions of the UPDATE, and is optional. If left as None, the SET conditions are determined from the bind parameters used during the compile phase of the UPDATE statement. If the bind parameters also are None during the compile phase, then the SET conditions will be generated from the full list of table columns.
If both values and compile-time bind parameters are present, the compile-time bind parameters override the information specified within values on a per-key basis.
The keys within values can be either Column objects or their string identifiers. Each key may reference one of:
If a SELECT statement is specified which references this UPDATE statement's table, the statement will be correlated against the UPDATE statement.
represent an alias, as typically applied to any table or sub-select within a SQL statement using the AS keyword (or without the keyword on certain databases such as Oracle).
this object is constructed from the alias() module level function as well as the alias() method available on all FromClause subclasses.
Represent an expression that is LEFT <operator> RIGHT.
Construct a new _BinaryExpression.
Represent a bind parameter.
Public constructor is the bindparam() function.
Construct a _BindParamClause.
Compare this _BindParamClause to the given clause.
Since compare() is meant to compare statement syntax, this method returns True if the two _BindParamClauses have just the same type.
Describe a calculated SQL expression that has a type, like CASE.
Extends ColumnElement to provide column-level comparison operators.
Base class for elements of a programmatically constructed SQL expression.
Returns the Engine or Connection to which this ClauseElement is bound, or None if none found.
Compare this ClauseElement to the given ClauseElement.
Subclasses should override the default behavior, which is a straight identity comparison.
Compile this SQL expression.
Uses the given Compiler, or the given AbstractDialect or Engine to create a Compiler. If no compiler arguments are given, tries to use the underlying Engine this ClauseElement is bound to to create a Compiler, if any.
Finally, if there is no bound Engine, uses an ANSIDialect to create a default Compiler.
parameters is a dictionary representing the default bind parameters to be used with the statement. If parameters is a list, it is assumed to be a list of dictionaries and the first dictionary in the list is used with which to compile against.
The bind parameters can in some cases determine the output of the compilation, such as for UPDATE and INSERT statements the bind parameters that are present determine the SET and VALUES clause of those statements.
return immediate child elements of this ClauseElement.
this is used for visit traversal.
**kwargs may contain flags that change the collection that is returned, for example to return a subset of items in order to cut down on larger traversals, or to return child items from a different context (such as schema-level collections instead of clause-level).
return a copy of this ClauseElement, with bindparam() elements replaced with values taken from the given dictionary.
e.g.:
>>> clause = column('x') + bindparam('foo') >>> print clause.compile().params {'foo':None} >>> print clause.params({'foo':7}).compile().params {'foo':7}
Compile and execute this ClauseElement, returning the result's scalar representation.
Return True if this clause element represents a complete executable statement.
same functionality as params(), except adds unique=True to affected bind parameters so that multiple statements can be used.
Describe a list of clauses, separated by an operator.
By default, is comma-separated, such as a column listing.
Compare this ClauseList to the given ClauseList, including a comparison of all the clause items.
Represent a dictionary/iterator of bind parameter key names/values.
Tracks the original _BindParamClause objects as well as the keys/position of each parameter, and can return parameters as a dictionary or a list. Will process parameter values according to the TypeEngine objects present in the _BindParamClause instances.
A class that knows how to traverse and visit ClauseElements.
Calls visit_XXX() methods dynamically generated for each particualr ClauseElement subclass encountered. Traversal of a hierarchy of ClauseElements is achieved via the traverse() method, which is passed the lead ClauseElement.
By default, ClauseVisitor traverses all elements fully. Options can be specified at the class level via the __traverse_options__ dictionary which will be passed to the get_children() method of each ClauseElement; these options can indicate modifications to the set of elements returned, such as to not return column collections (column_collections=False) or to return Schema-level items (schema_visitor=True).
ClauseVisitor also supports a simultaneous copy-and-traverse operation, which will produce a copy of a given ClauseElement structure while at the same time allowing ClauseVisitor subclasses to modify the new structure in-place.
'chain' an additional ClauseVisitor onto this ClauseVisitor.
the chained visitor will receive all visit events after this one.
Represents a generic column expression from any textual string. This includes columns associated with tables, aliases and select statements, but also any arbitrary text. May or may not be bound to an underlying Selectable. _ColumnClause is usually created publically via the column() function or the literal_column() function.
- text
- the text of the element.
- selectable
- parent selectable.
- type
- TypeEngine object which can associate this _ColumnClause with a type.
- is_literal
- if True, the _ColumnClause is assumed to be an exact expression that will be delivered to the output with no quoting rules applied regardless of case sensitive settings. the literal_column() function is usually used to create such a _ColumnClause.
Construct a new _ColumnClause.
An ordered dictionary that stores a list of ColumnElement instances.
Overrides the __eq__() method to produce SQL clauses between sets of correlated columns.
Add a column to this collection.
The key attribute of the column will be used as the hash key for this dictionary.
Represent an element that is useable within the "column clause" portion of a SELECT statement.
This includes columns associated with tables, aliases, and subqueries, expressions, function calls, SQL keywords such as NULL, literals, etc. ColumnElement is the ultimate base class for all such elements.
ColumnElement supports the ability to be a proxy element, which indicates that the ColumnElement may be associated with a Selectable which was derived from another Selectable. An example of a "derived" Selectable is an Alias of a Table.
a ColumnElement, by subclassing the _CompareMixin mixin class, provides the ability to generate new ClauseElement objects using Python expressions. See the _CompareMixin docstring for more details.
Foreign key accessor. References a list of ForeignKey objects which each represent a foreign key placed on this column's ultimate ancestor.
A Set containing TableClause-bound, non-proxied ColumnElements for which this ColumnElement is a proxy. In all cases except for a column proxied from a Union (i.e. CompoundSelect), this set will be just one element.
Primary key flag. Indicates if this Column represents part or whole of a primary key for its parent table.
Return True if the given ColumnElement has a common ancestor to this ColumnElement.
adapts a ClauseElement which may or may not be a ColumnElement subclass itself into an object which acts like a ColumnElement.
Defines comparison and math operations for ClauseElement instances.
produce a BETWEEN clause, i.e. <column> BETWEEN <cleft> AND <cright>
Allow _CompareMixins to return the underlying ClauseElement, for non-ClauseElement _CompareMixins.
Allow _CompareMixins to return the appropriate object to be used in expressions.
produce a generic operator function.
e.g.
somecolumn.op("*")(5)
produces
somecolumn * 5
Represent an element that can be used within the FROM clause of a SELECT statement.
Given a ColumnElement, return the exported ColumnElement object from this Selectable which corresponds to that original Column via a common anscestor column.
return True if this FromClause is 'derived' from the given FromClause.
An example would be an Alias of a Table is derived from that Table.
True if the name of this FromClause may be prepended to a column in a generated SQL statement.
A dictionary mapping an original Table-bound column to a proxied column in this FromClause.
replace all occurences of FromClause 'old' with the given Alias object, returning a copy of this FromClause.
Describe a SQL function.
Extends _CalculatedClause, turn the clauselist into function arguments, also adds a packagenames argument.
Generate _Function objects based on getattr calls.
represent a grouping within a column expression
represent a JOIN construct between two FromClause elements.
the public constructor function for Join is the module-level join() function, as well as the join() method available off all FromClause subclasses.
Create a Select out of this Join clause and return an Alias of it.
The Select is not correlating.
Returns the column list of this Join with all equivalently-named, equated columns folded into one column, where 'equated' means they are equated to each other in the ON clause of this join.
Create a Select from this Join.
represent a label, as typically applied to any column-level element using the AS sql keyword.
this object is constructed from the label() module level function as well as the label() method available on all ColumnElement subclasses.
a ClauseVisitor that will not traverse the exported Column collections on Table, Alias, Select, and CompoundSelect objects (i.e. their 'columns' or 'c' attribute).
this is useful because most traversals don't need those columns, or in the case of ANSICompiler it traverses them explicitly; so skipping their traversal here greatly cuts down on method call overhead.
Represent the NULL keyword in a SQL statement.
Public constructor is the null() function.
Represent a SELECT statement, with appendable clauses, as well as the ability to execute itself and return a result set.
construct a Select object.
The public constructor for Select is the select() function; see that function for argument descriptions.
Return a list of all FromClause elements which will be applied to the FROM clause of the resulting statement.
Base class for Select and CompoundSelects.
Construct a new _SelectBaseMixin.
Represent a column list-holding object.
this is the common base class of ColumnElement and FromClause. The reason ColumnElement is marked as a "list-holding" object is so that it can be treated similarly to FromClause in column-selection scenarios; it contains a list of columns consisting of itself.
a ColumnCollection containing ColumnElement instances.
represents a "table" construct.
Note that this represents tables only as another syntactical construct within SQL expressions; it does not provide schema-level functionality.
Represent a literal SQL text fragment.
Public constructor is the text() function.
Handle a type keyword in a SQL statement.
Used by the Case statement.
Construct a new _UnaryExpression.
Form the base for INSERT, UPDATE, and DELETE statements.