如何计算表中包含PK（PL-SQL）的列数

Question

INTRODUCTION

I came across this exercise which ask me to write a script which counts how many rows there are, count how many columns, with PKs, there are and the storage consumed.

Reading the docs I came across this useful line:

ANALYZE TABLE table_name COMPUTE STATISTICS FOR TABLE;

This line gathers statistics of a given table_name which then can be accessed as such:

SELECT *
FROM user_tables
WHERE table_name LIKE 'table_name'

Here it displays a lot from the table we previously inputted but I can't find the number of columns which have PKs and the storage consumed by such table.

My TRY AT PL-SQL is:

DECLARE

    v_nom_table VARCHAR2(10);
    v_num_rows NUMBER(100);
    v_num_col_pk NUMBER(100);
    v_num_storage NUMBER(100);

BEGIN

    v_nom_table := &input_nom_table;

    ANALYZE TABLE v_nom_table COMPUTE STATISTICS FOR TABLE;

    SELECT num_row INTO v_num_rows 
    FROM user_tables
    WHERE UPPER(table_name) LIKE UPPER(v_nom_table )

    DBMS_OUTPUT.PUT_LINE(
        'La tabla ' || v_nom_table || ' tiene: ' || v_num_rows || ' filas, ' 
         || v_num_col_pk || ' columnas con PK y ocupa ' || v_num_storage
    );

QUESTION

How do I get the number of columns involved in PK and the storage consumed by the given table?

Answer 1

A typical solution to list the columns involved in the primary key of a table is to:

• query Oracle views USER_CONSTRAINTS (or ALL_CONSTRAINTS ) to find the record that relates to the primary key ( CONSTRAINT_TYPE = P ) of thet table
• then lookup the related columns in view USER_CONS_COLUMNS

Consider:

SELECT COUNT(*)
FROM user_constraints cons
INNER JOIN user_cons_columns cols ON cons.constraint_name = cols.constraint_name
WHERE cons.constraint_type = 'P' AND cons.table_name = ?

---

When it comes to computing the storage space consumed by a given table, that's a different question. A solution is to use column BLOCKS from view USER_TABLES . THen all you have to do is multiply this value by the block size of the tablespace in which the table is stored in the ALL_TABLESPACES view, in column BLOCK_SIZE .