natural_key: Create SQL string for joining on matching natural keys
In UweBlock/lazysql: Lazy SQL Programming

Description Usage Arguments Details Value Note Author(s) See Also Examples

Create string with SQL expressions for WHERE clause to join two tables on the given columns.

1	natural_key(table_names, key_columns)

`table_names`	[character(2)] Name of data base tables to be joined.
`key_columns`	[character(1:Inf)] Names of key columns in both tables.

The names of tables and key columns must be valid SQL identifiers. They are validated to conform to the regular expression returned by valid_identifier_regex.

The SQL string is created in 3 steps:

Combine table names with key names, eg, "PRL.FLIGHT_NR".
Create logical expressions, eg, "PRL.FLIGHT_NR = PRL_SSR.FLIGHT_NR"
Concatenate logical expressions by "and" to form final SQL esxpression.

Character string to be used in SQL statement.

The current implementation assumes that key columns have the same names in both tables.

Uwe Block

valid_identifier_regex.

# SQL expression
(sql_expr <- lazysql::natural_key(c("TAB1", "tab_2"),c("COL1", "col_2")))

# sample SQL JOIN statement
paste("select * from TAB1, TAB2 where", sql_expr)