PostgreSQL Query Catalog

Find base tables that implement many-to-many relationship types that do not permit repeating relationships. More specifically find tables that have two or more foreign keys and all the columns of the table are either foreign key columns or a surrogate key column. It could be that during the system analysis a mistake has been made and some attributes of the entity type that represents the relationship type have not been discovered.

Find base tables that implement many-to-many relationship types that do not permit repeating relationships. More specifically find tables that have two or more foreign keys and all the columns of the table belong to a foreign key. In addition, all the table columns must be covered by a primary key or unique constraint. It could be that during the system analysis a mistake has been made and some attributes of the entity type that represents the relationship type have not been discovered.

Find base tables that implement recording multivalued attribute values with the help of repeating group of columns. Find base tables that have more than one columns with the same type and field size and the difference between the columns are the numbers in the column names (column1, column2, etc.).

Find base tables that name starts with a prefix. Do not use prefixes in case of base table names. Derive the names from the names of entity types. Do not use "_", "t_", "tab_", "t11_" etc as prefixes of a table.

Find base tables where all he non-primary key columns are optional. Avoid too many optional columns. You have to be extra careful with NULLs in case of formulating search conditions of data manipulation statements.

Find base tables where all the columns are optional, i.e., permit NULLs. In such tables can be rows with no identity value and thus indistinguishable from other rows.

Find base tables where all the columns have a default value.

Find base tables where all unique keys (sets of columns covered by a unique constraint, or a unique index) have at least one optional column. In this case there can be rows in the table where the values that should identify the row are missing. Because NULL is not a value and is not duplicate of another NULL the, follwing is possible: CREATE TABLE Uniq(a INTEGER NOT NULL,
b INTEGER,
CONSTRAINT ak_uniq UNIQUE (a, b));

INSERT INTO Uniq(a, b) VALUES (1, NULL);
INSERT INTO Uniq(a, b) VALUES (1, NULL);

Find base tables where more than one column gets the default value by using the sequence generator mechanism.

Find base tables where multiple columns are associated with a sequence generator. Do not create unnecessary sequence generators. If one uses in a table a surrogate key, then it is enough to have one column where the values are generated by using a (external or internal) sequence generator.

Find base tables where statistics has not been collected at all or it has been lastly collected more than 40 days ago.

Find base tables where the number of rows is zero. If there are no rows in a table, then it may mean that one hasn't tested constraints that have been declared to the table or implemented by using triggers. It could also mean that the table is not needed because there is no data that should be registered in the table.

Find base tables where uniqueness is achieved by using only unique indexes, i.e., there is at least one unique index but no uniqueness constraints (PRIMARY KEY, UNIQUE, EXCLUDE)

Find base tables with more than one comment columns

Find base tables with more than one name columns. Perhaps the normalization level of the table is low.

Find base tables without any unique constraints and primary key as well as any unique index, whether it is created explicitly by a developer or automatically by the DBMS. The only legitimate reason of such a table is if it is an abstract table that is used to define common columns of subtables.

Find base tables without any unique constraints and the primary key. In such tables there are no restrictions for recording duplicate rows. Each row represents a true proposition about the real world. It does not make the proposition truer if one presents it more than once. Moreover, duplicate rows increase data size. Without keys the DBMS lacks vital information about data in the database that it can internally use to choose better execution plans and in this way improve performance of database operations. The only legitimate reason of such a table is if it is an abstract table that is used to define common columns of subtables.

Find Boolean expressions, queries, routines, and default values that refer to value 'NULL'. Perhaps NULL was intended instead. 'NULL' is a string (a value) but NULL is a special marker for denoting missing value.

Find candidate key columns with the names like id, identifikaator, code, kood, number, etc. The names should have a prefix or a suffix. These are too generic names.

Find cases where a base table has been split horizontally into multiple smaller base tables based on the distinct values in one of the columns of the original table. Each such newly created table has the name, a part of which is a data value from the original tables. Find base tables that have the same columns (column name, column order, data type) and the difference between the tables are the numbers in the table names (table1, table2, etc.).