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sqlinnerjoin

Inner join between two PostgreSQL database tables

Description

example

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.

example

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

Examples

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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)

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)

Input Arguments

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

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

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 Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

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.

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

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

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

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, 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

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

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

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

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

Output Arguments

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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.

PostgreSQL Data TypeMATLAB Data Type

Boolean

logical

Smallint

double

Integer

double

Bigint

double

Decimal

double

Numeric

double

Real

double

Double precision

double

Smallserial

double

Serial

double

Bigserial

double

Money

double

Varchar

string

Char

string

Text

string

Bytea

string

Timestamp

datetime

Timestampz

datetime

Abstime

datetime

Date

datetime

Time

duration

Timez

duration

Interval

calendarDuration

Reltime

calendarDuration

Enum

categorical

Cidr

string

Inet

string

Macaddr

string

Uuid

string

Xml

string

Limitations

The name-value pair argument 'VariableNamingRule' has these limitations when 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.

Introduced in R2020b