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POSQL code to check for Many-To-Many relationships
 

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  1. POSQL code to check for Many-To-Many relationships
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    <p>I have been researching non-stop and have only managed to find out - how to check for a 1-To-Many relationship in SQL. I want to know if anyone can help me find out on how to check for a Many-To-Many relationship in SQL code. The tables in the database are in correct normal form.</p> <p>The scenario I have is:</p> <ul> <li>A user will select three tables from the database.</li> <li>Once the three tables have been selected, I need to check if those tables have a Many-To-Many relationship.</li> <li>So I need to check if the three tables that the user has selected are associated with a primary key and the intersection table has the two reference keys that point to the two other tables.</li> </ul> <p><code></code></p> <pre><code>SELECT K_Table = FK.TABLE_NAME, FK_Column = CU.COLUMN_NAME, PK_Table = PK.TABLE_NAME, PK_Column = PT.COLUMN_NAME, Constraint_Name = C.CONSTRAINT_NAME FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS FK ON C.CONSTRAINT_NAME = FK.CONSTRAINT_NAME INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS PK ON C.UNIQUE_CONSTRAINT_NAME = PK.CONSTRAINT_NAME INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE CU ON C.CONSTRAINT_NAME = CU.CONSTRAINT_NAME INNER JOIN (SELECT i1.TABLE_NAME, i2.COLUMN_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS i1 INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE i2 ON i1.CONSTRAINT_NAME = i2.CONSTRAINT_NAME WHERE i1.CONSTRAINT_TYPE = 'PRIMARY KEY') PT ON PT.TABLE_NAME = PK.TABLE_NAME WHERE PK.TABLE_NAME = '" + ActionM2M.Table2 + "' AND FK.TABLE_NAME = '" + ActionM2M.ITableNames1 + "' AND exists (SELECT K_Table = FK.TABLE_NAME, FK_Column = CU.COLUMN_NAME, PK_Table = PK.TABLE_NAME, PK_Column = PT.COLUMN_NAME, Constraint_Name = C.CONSTRAINT_NAME FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS FK ON C.CONSTRAINT_NAME = FK.CONSTRAINT_NAME INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS PK ON C.UNIQUE_CONSTRAINT_NAME = PK.CONSTRAINT_NAME INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE CU ON C.CONSTRAINT_NAME = CU.CONSTRAINT_NAME INNER JOIN (SELECT i1.TABLE_NAME, i2.COLUMN_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS i1 INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE i2 ON i1.CONSTRAINT_NAME = i2.CONSTRAINT_NAME WHERE i1.CONSTRAINT_TYPE = 'PRIMARY KEY') PT ON PT.TABLE_NAME = PK.TABLE_NAME WHERE PK.TABLE_NAME = '" + ActionM2M.Table1 + "' AND FK.TABLE_NAME = '" + ActionM2M.ITableNames1 + "') </code></pre>
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    1. USJosef K
    1. USSpaceApple
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    1. COCan you explain what you've got? Do you have a single table and you are trying to analyze it to see whether it is in a correct normal form? Or do you have multiple tables and you're trying to see whether one is an association table (or junction table) with a primary key that contains two references to other tables? What is the purpose of trying to find the many-to-many relationships?
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      1. POSQL code to check for Many-To-Many relationships
      1. USJonathan Leffler
    2. COThis answer should be of help: http://stackoverflow.com/questions/786918/many-to-many-relationship-use-associative-table-or-delimited-values-in-a-column
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      1. POSQL code to check for Many-To-Many relationships
      1. USRaymond Hettinger
    3. COThe tables in the database are in correct normal form. The scenario i have is : A user will select three tables from the database, once the three tables have been selected i need to check if those tables have a Many-To-Many relationship. so i need to check if those three tables that the user has selected are associated with a primary key and the intersection table has the two reference keys that point to the two other tables. I hope i have explained enough.
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      1. USSpaceApple
 

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