sqlinnerjoin

Inner join between two PostgreSQL database tables

Since R2020b

Syntax

data = sqlinnerjoin(conn,lefttable,righttable)

data = sqlinnerjoin(conn,lefttable,righttable,Name,Value)

Description

data = sqlinnerjoin(conn,lefttable,righttable) returns a table resulting from an inner join between the left and right database tables. This function matches rows using all shared columns, or keys, in both database tables. The inner join retains only the rows that match between the two tables. Executing this function is the equivalent of writing the SQL statement SELECT * FROM lefttable,righttable INNER JOIN lefttable.key = righttable.key.

data = sqlinnerjoin(conn,lefttable,righttable,Name,Value) uses additional options specified by one or more name-value arguments. For example, specify Keys = "productNumber" to use the productNumber column as a key for joining the two database tables.

Examples

Join Two Database Tables Using PostgreSQL Native Interface

Use a PostgreSQL native interface database connection to import product data from an inner join between two PostgreSQL database tables into MATLAB®.

Create a PostgreSQL native interface database connection to a PostgreSQL database using the data source name, user name, and password. The database contains the tables productTable and suppliers.

datasource = "PostgreSQLDataSource";
username = "dbdev";
password = "matlab";
conn = postgresql(datasource,username,password);

Join two database tables, productTable and suppliers. The productTable table is the left table of the join, and the suppliers table is the right table of the join. The sqlinnerjoin function automatically detects the shared column between the tables. data is a table that contains the matched rows from the two tables.

lefttable = "productTable";
righttable = "suppliers";
data = sqlinnerjoin(conn,lefttable,righttable);

Display the first three rows of matched data. The columns from the right table (suppliers) appear to the right of the columns from the left table (productTable).

head(data,3)

ans=3×10 table
    productnumber    stocknumber    suppliernumber    unitcost    productdescription    suppliernumber_1      suppliername          city           country           faxnumber   
    _____________    ___________    ______________    ________    __________________    ________________    _________________    __________    ________________    ______________

          1          4.0035e+05          1001            14       "Building Blocks"           1001          "Wonder Products"    "New York"    "United States"     "212 435 1617"
          2          4.0031e+05          1002             9       "Painting Set"              1002          "Terrific Toys"      "London"      "United Kingdom"    "44 456 9345" 
          3            4.01e+05          1009            17       "Slinky"                    1009          "Doll's Galore"      "London"      "United Kingdom"    "44 222 2397" 

Close the database connection.

close(conn)

Specify Key for Joining Two Database Tables

Use a PostgreSQL native interface database connection to import joined product data from two PostgreSQL database tables into MATLAB®. Specify the key to use for joining the tables.

Create a PostgreSQL native interface database connection to a PostgreSQL database using the data source name, user name, and password. The database contains the tables productTable and suppliers.

datasource = "PostgreSQLDataSource";
username = "dbdev";
password = "matlab";
conn = postgresql(datasource,username,password);

Join two database tables, productTable and suppliers. The productTable table is the left table of the join, and the suppliers table is the right table of the join. Specify the key, or shared column, between the tables using the 'Keys' name-value pair argument. data is a table that contains the matched rows from the two tables.

lefttable = "productTable";
righttable = "suppliers";
data = sqlinnerjoin(conn,lefttable,righttable,'Keys',"supplierNumber");

Display the first three rows of matched data. The columns from the right table (suppliers) appear to the right of the columns from the left table (productTable).

head(data,3)

ans=3×10 table
    productnumber    stocknumber    suppliernumber    unitcost    productdescription    suppliernumber_1      suppliername          city           country           faxnumber   
    _____________    ___________    ______________    ________    __________________    ________________    _________________    __________    ________________    ______________

          1          4.0035e+05          1001            14       "Building Blocks"           1001          "Wonder Products"    "New York"    "United States"     "212 435 1617"
          2          4.0031e+05          1002             9       "Painting Set"              1002          "Terrific Toys"      "London"      "United Kingdom"    "44 456 9345" 
          3            4.01e+05          1009            17       "Slinky"                    1009          "Doll's Galore"      "London"      "United Kingdom"    "44 222 2397" 

Close the database connection.

close(conn)

Filter Rows in Joined Data

Use a PostgreSQL native interface database connection to import joined product data from two PostgreSQL database tables into MATLAB®. Specify the row filter condition to use for joining the tables.

Create a PostgreSQL native interface database connection to a PostgreSQL database using the data source name, username, and password. The database contains the tables productTable and suppliers.

datasource = "PostgreSQLDataSource";
username = "dbdev";
password = "matlab";
conn = postgresql(datasource,username,password);

Join the two database tables, productTable and suppliers. The productTable table is the left table of the join, and the suppliers table is the right table of the join. The table data contains the matched rows from the two tables.

lefttable = "productTable";
righttable = "suppliers";
data = sqlinnerjoin(conn,lefttable,righttable);

Display the first five rows of matched data. The columns from the right table appear to the right of the columns from the left table.

head(data,5)

    productnumber    stocknumber    suppliernumber    unitcost    productdescription    suppliernumber_1          suppliername              city           country           faxnumber   
    _____________    ___________    ______________    ________    __________________    ________________    _________________________    __________    ________________    ______________

          1          4.0034e+05          1001            14       "Building Blocks"           1001          "Wonder Products"            "New York"    "United States"     "212 435 1617"
          2          4.0031e+05          1002             9       "Painting Set"              1002          "Terrific Toys"              "London"      "United Kingdom"    "44 456 9345" 
          3            4.01e+05          1009            17       "Slinky"                    1009          "Doll's Galore"              "London"      "United Kingdom"    "44 222 2397" 
          4          4.0034e+05          1008            21       "Space Cruiser"             1008          "The Great Train Company"    "Nashua"      "United States"     "403 121 3478"
          5          4.0046e+05          1005             3       "Tin Soldier"               1005          "Custers Tin Soldiers"       "Boston"      "United States"     "617 939 1234"

Join the same tables, but this time use a row filter. The filter condition is that unitCost must be less than 15. Again, display the first five rows of matched data.

rf = rowfilter("unitCost");
rf = rf.unitCost <= 15;
data = sqlinnerjoin(conn,lefttable,righttable,"RowFilter",rf);
head(data,5)

    productnumber    stocknumber    suppliernumber    unitcost    productdescription    suppliernumber_1         suppliername            city           country           faxnumber   
    _____________    ___________    ______________    ________    __________________    ________________    ______________________    __________    ________________    ______________

          1          4.0034e+05          1001            14       "Building Blocks"           1001          "Wonder Products"         "New York"    "United States"     "212 435 1617"
          2          4.0031e+05          1002             9       "Painting Set"              1002          "Terrific Toys"           "London"      "United Kingdom"    "44 456 9345" 
          5          4.0046e+05          1005             3       "Tin Soldier"               1005          "Custers Tin Soldiers"    "Boston"      "United States"     "617 939 1234"
          6          4.0088e+05          1004             8       "Sail Boat"                 1004          "Incredible Machines"     "Dublin"      "Ireland"           "01 222 3456" 
          8          2.1257e+05          1001             5       "Train Set"                 1001          "Wonder Products"         "New York"    "United States"     "212 435 1617"

Close the database connection.

close(conn)

Input Arguments

conn — PostgreSQL native interface database connection

connection object

PostgreSQL native interface database connection, specified as a connection object.

lefttable — Left table

character vector | string scalar

Left table, specified as a character vector or string scalar. Specify the name of the database table on the left side of the join.

Example: 'inventoryTable'

Data Types: char | string

righttable — Right table

character vector | string scalar

Right table, specified as a character vector or string scalar. Specify the name of the database table on the right side of the join.

Example: 'productTable'

Data Types: char | string

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: data = sqlinnerjoin(conn,"productTable","suppliers",'LeftCatalog',"toystore_doc",'LeftSchema',"dbo",'RightCatalog',"toy_shop",'RightSchema',"toys",'MaxRows',5) performs an inner join between left and right tables by specifying the catalog and schema for both tables and returns five matched rows.

LeftCatalog — Left catalog

character vector | string scalar

Left catalog, specified as the comma-separated pair consisting of 'LeftCatalog' and a character vector or string scalar. Specify the database catalog name where the left table of the join is stored.

Example: 'LeftCatalog','toy_store'

Data Types: char | string

RightCatalog — Right catalog

character vector | string scalar

Right catalog, specified as the comma-separated pair consisting of 'RightCatalog' and a character vector or string scalar. Specify the database catalog name where the right table of the join is stored.

Example: 'RightCatalog','toy_store'

Data Types: char | string

LeftSchema — Left schema

character vector | string scalar

Left schema, specified as the comma-separated pair consisting of 'LeftSchema' and a character vector or string scalar. Specify the database schema name where the left table of the join is stored.

Example: 'LeftSchema','dbo'

Data Types: char | string

RightSchema — Right schema

character vector | string scalar

Right schema, specified as the comma-separated pair consisting of 'RightSchema' and a character vector or string scalar. Specify the database schema name where the right table of the join is stored.

Example: 'RightSchema','dbo'

Data Types: char | string

Keys — Keys

character vector | string scalar | cell array of character vectors | string array

Keys, specified as the comma-separated pair consisting of 'Keys' and a character vector, string scalar, cell array of character vectors, or string array. Specify a character vector or string scalar to indicate one key. For multiple keys, specify a cell array of character vectors or a string array. Use this name-value pair argument to identify the shared keys (columns) between the two tables to join.

You cannot use this name-value pair argument with the 'LeftKeys' and 'RightKeys' name-value pair arguments.

Example: 'Keys','MANAGER_ID'

Data Types: char | string | cell

LeftKeys — Left keys

character vector | string scalar | cell array of character vectors | string array

Left keys, specified as the comma-separated pair consisting of 'LeftKeys' and a character vector, string scalar, cell array of character vectors, or string array. Specify a character vector or string scalar to indicate one key. For multiple keys, specify a cell array of character vectors or a string array. This name-value pair argument identifies the keys in the left table for the join to the right table.

Use this name-value pair argument with the 'RightKeys' name-value pair argument. Both arguments must specify the same number of keys. The sqlinnerjoin function pairs the values of the keys based on their order.

Example: 'LeftKeys',["productNumber" "Price"],'RightKeys',["productNumber" "Price"]

Data Types: char | string | cell

RightKeys — Right keys

character vector | string scalar | cell array of character vectors | string array

Right keys, specified as the comma-separated pair consisting of 'RightKeys' and a character vector, string scalar, cell array of character vectors, or string array. Specify a character vector or string scalar to indicate one key. For multiple keys, specify a cell array of character vectors or a string array. This name-value pair argument identifies the keys in the right table for the join to the left table.

Use this name-value pair argument with the 'LeftKeys' name-value pair argument. Both arguments must specify the same number of keys. The sqlinnerjoin function pairs the values of the keys based on their order.

Example: 'LeftKeys',["productIdentifier" "Cost"],'RightKeys',["productNumber" "Price"]

Data Types: char | string | cell

MaxRows — Maximum number of rows to return

positive numeric scalar

Maximum number of rows to return, specified as the comma-separated pair consisting of 'MaxRows' and a positive numeric scalar. By default, the sqlinnerjoin function returns all rows from the executed SQL query. Use this name-value pair argument to limit the number of rows imported into MATLAB^®.

Example: 'MaxRows',10

Data Types: double

VariableNamingRule — Variable naming rule

"preserve" (default) | "modify"

Variable naming rule, specified as the comma-separated pair consisting of 'VariableNamingRule' and one of these values:

• "preserve" — Preserve most variable names when the sqlinnerjoin function imports data. For details, see the Limitations section.

• "modify" — Remove non-ASCII characters from variable names when the sqlinnerjoin function imports data.

Example: 'VariableNamingRule',"modify"

Data Types: string

RowFilter — Row filter condition

<unconstrained> (default) | matlab.io.RowFilter object

Row filter condition, specified as a matlab.io.RowFilter object.

Example: rf = rowfilter("productnumber"); rf = rf.productnumber <= 5; sqlinnerjoin(conn,lefttable,righttable,"RowFilter",rf)

Output Arguments

data — Joined data

table

Joined data, returned as a table that contains the matched rows from the join of the left and right tables. data also contains a variable for each column in the left and right tables.

If the column names are shared between the joined database tables and have the same case, then the sqlinnerjoin function adds a unique suffix to the corresponding variable names in data.

When you import data, the sqlinnerjoin function converts the data type of each column from the PostgreSQL database to the MATLAB data type. This table maps the data type of a database column to the converted MATLAB data type. The first and second columns contain the scalar data type mappings, whereas the third and fourth columns contain the array data type mappings.

Details for how MATLAB reads PostgreSQL array types consist of the following:

• MATLAB reads columns of PostgreSQL array types into cell arrays. The dimensions of the array in each cell match the dimension of the array stored in the PostgreSQL database table row.

• The data of the arrays in the MATLAB cell arrays depends on the underlying data in the PostgreSQL arrays.

• The default data type of each PostgreSQL array type matches its scalar equivalent.

Scalar Data Type Mappings		Array Data Type Mappings (since R2024b)
PostgreSQL	MATLAB	PostgreSQL	MATLAB
Boolean	logical	Boolean []	Cell array of logical values
Smallint	double	Smallint []	Cell array of double values
Integer	double	Integer []	Cell array of double values
Bigint	double	Bigint []	Cell array of double values
Decimal	double	Decimal []	Cell array of double values
Numeric	double	Numeric []	Cell array of double values
Real	double	Real []	Cell array of double values
Double precision	double	Double precision []	Cell array of double values
Smallserial	double	N/A	N/A
Serial	double	N/A	N/A
Bigserial	double	N/A	N/A
Money	double	Money []	Cell array of double values
Varchar	string	Varchar []	Cell array of strings
Char	string	Char []	Cell array of strings
Text	string	Text []	Cell array of strings
Bytea	string	Bytea []	Cell array of strings
Timestamp	datetime	Timestamp []	Cell array of datetimes
Timestampz	datetime	Timestampz []	Cell array of datetimes
Abstime	datetime	Abstime []	Cell array of datetimes
Date	datetime	Date []	Cell array of datetimes
Time	duration	Time []	Cell array of durations
Timez	duration	Timez []	Cell array of durations
Interval	calendarDuration	Interval []	Cell array of calendarDurations
Reltime	calendarDuration	Reltime []	Cell array of calendarDurations
Enum	categorical	Enum []	Cell array of categoricals
Cidr	string	Cidr []	Cell array of strings
Inet	string	Inet []	Cell array of strings
Macaddr	string	Macaddr []	Cell array of strings
Uuid	string	Uuid []	Cell array of strings
Xml	string	Xml []	Cell array of strings

Limitations

The name-value argument VariableNamingRule has these limitations if it is set to the value "modify":

• The variable names Properties, RowNames, and VariableNames are reserved identifiers for the table data type.

• The length of each variable name must be less than the number returned by namelengthmax.

Version History

Introduced in R2020b

R2024b: Support for reading array types

You can now read array types without any extra data conversions.

R2023a: Selectively join data based on filter condition

You can use the RowFilter when joining data from database tables.