Package org.linuxforhealth.fhir.database.utils.query

Class SelectAdapter

java.lang.Object

org.linuxforhealth.fhir.database.utils.query.SelectAdapter

Direct Known Subclasses:

FromSubQueryAdapter

public class SelectAdapter
extends java.lang.Object

An abstract representation of a select statement which can be translated into an executable select statement. Keeps track of bind variables (parameter markers) and hopefully is a bit easier to use (and is more reliable) than constructing SQL with StringBuilder. The goal is to support two main use-cases (which drive the API design):

• 1. Simplify construction of hand-written SQL statements
• 2. Support code-generated SQL where a statement is constructed from another model (e.g. FHIR search queries).

The goal isn't to enforce building a syntactically perfect SQL statement - checking that is the role of the RDBMS SQL parser. But hopefully this makes things a bit easier, less error-prone and therefore quicker. It also helps to standardize the SQL statement building process across the project.

Constructor Summary

Constructors

Constructor	Description
SelectAdapter(boolean distinct, java.lang.String... columns)
SelectAdapter(java.lang.String... columns)	Public constructor taking a collection of string column names
SelectAdapter(Select select)	Adapter this select statement

Method Summary

Modifier and Type	Method	Description
SelectAdapter	addColumn(java.lang.String source, java.lang.String name, Alias alias)
SelectAdapter	addColumn(java.lang.String columnValue, Alias alias)	Add a column value with a given alias.
Select	build()	Get the statement we've been constructing
SelectAdapter	column(java.lang.String source, java.lang.String name)
FromAdapter	from()	Create a FromAdapter associated with the current select statement.
FromAdapter	from(java.lang.String table)	Create a from clause for this select statement
FromAdapter	from(java.lang.String tableName, Alias alias)	Create a from clause for this select statement
FromAdapter	from(Select sub, Alias alias)	Add the sub-query select to the FROM clause
Select	getSelect()	Getter for the select statement we are managing
void	pagination(int offset, int rowsPerPage)	Add pagination offset/limit to the query
void	union(Select unionSelect)	Add a select via UNION
void	unionAll(Select unionAllSelect)	Add a select via UNION ALL
SelectAdapter	with(Select selectClause, Alias alias)	Add a WITH x AS (SELECT ...) statement to the beginning of the select

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SelectAdapter

public SelectAdapter(Select select)

Adapter this select statement

Parameters:

select -

SelectAdapter

public SelectAdapter(java.lang.String... columns)

Public constructor taking a collection of string column names

Parameters:

columns -

SelectAdapter

public SelectAdapter(boolean distinct,
                     java.lang.String... columns)

Method Detail

column

public SelectAdapter column(java.lang.String source,
                            java.lang.String name)

addColumn

public SelectAdapter addColumn(java.lang.String source,
                               java.lang.String name,
                               Alias alias)

addColumn

public SelectAdapter addColumn(java.lang.String columnValue,
                               Alias alias)

Add a column value with a given alias. Can be used to add literals in the select list

Parameters:

source -

name -

alias -

Returns:

with

public SelectAdapter with(Select selectClause,
                          Alias alias)

Add a WITH x AS (SELECT ...) statement to the beginning of the select

Parameters:

selectClause -

alias -

Returns:

from

public FromAdapter from(java.lang.String tableName,
                        Alias alias)

Create a from clause for this select statement

Returns:

from

public FromAdapter from(Select sub,
                        Alias alias)

Add the sub-query select to the FROM clause

Parameters:

sub - the sub-query select statement

alias -

Returns:

from

public FromAdapter from(java.lang.String table)

Create a from clause for this select statement

Returns:

from

public FromAdapter from()

Create a FromAdapter associated with the current select statement. No row sources are added to the query. The FROM will only be added to the statement if rows sources are subsequently added to the returned FromAdapter.

Returns:

getSelect

public Select getSelect()

Getter for the select statement we are managing

Returns:

pagination

public void pagination(int offset,
                       int rowsPerPage)

Add pagination offset/limit to the query

Parameters:

translator -

offset -

rowsPerPage -

union

public void union(Select unionSelect)

Add a select via UNION

Parameters:

unionSelect - the select to be UNION'd to this select statement

unionAll

public void unionAll(Select unionAllSelect)

Add a select via UNION ALL

Parameters:

unionAllSelect - the select to be UNION ALL'd to this select statement

build

public Select build()

Get the statement we've been constructing

Returns: