Fetch Table Name from a Column for from Clause

fetch table name from a column for from clause

@Akshay,

Please find the code below for your reference.

Create or replace procedure create_cursor is
l_statement varchar2(32767);
cursor v_records is
  select * from t;
begin
for temp in v_records
loop
  l_statement := 'INSERT INTO myTable (id, name) select '||temp.id||','
   ||temp.name|| ' from ' || temp.table1 
   || ' where ' || temp.where_clause;

  execute immediate l_statement;
  end loop;
end;
/

How can I get column names from a table in SQL Server?

You can obtain this information and much, much more by querying the Information Schema views.

This sample query:

SELECT *
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = N'Customers'

Can be made over all these DB objects:

• CHECK_CONSTRAINTS
• COLUMN_DOMAIN_USAGE
• COLUMN_PRIVILEGES
• COLUMNS
• CONSTRAINT_COLUMN_USAGE
• CONSTRAINT_TABLE_USAGE
• DOMAIN_CONSTRAINTS
• DOMAINS
• KEY_COLUMN_USAGE
• PARAMETERS
• REFERENTIAL_CONSTRAINTS
• ROUTINES
• ROUTINE_COLUMNS
• SCHEMATA
• TABLE_CONSTRAINTS
• TABLE_PRIVILEGES
• TABLES
• VIEW_COLUMN_USAGE
• VIEW_TABLE_USAGE
• VIEWS

python library for extracting table names from from clause in SQL Statetments,

You can use sqlparse with a recursive generator function:

import sqlparse, re
def get_tables(d):
    f = False
    for i in getattr(d, 'tokens', []):
       if isinstance(i, sqlparse.sql.Token) and i.value.lower() == 'from':
          f = True
       elif isinstance(i, (sqlparse.sql.Identifier, sqlparse.sql.IdentifierList)) and f:
          f = False
          if not any(isinstance(x, sqlparse.sql.Parenthesis) or 'select' in x.value.lower() for x in getattr(i, 'tokens', [])):
             fr = ''.join(str(j) for j in i if j.value not in {'as', '\n'})
             for t in re.findall('(?:\w+\.\w+|\w+)\s+\w+|(?:\w+\.\w+|\w+)', fr):
                yield {'table':(t1:=t.split())[0], 'alias':None if len(t1) < 2 else t1[-1]}
       yield from get_tables(i)

print(list(get_tables(sqlparse.parse(s)[0])))

Output:

[{'table': 'PIMSCS.HISTPREPRO', 'alias': 'OBJ'}, {'table': 'PIMSCS.ESTAGIOS', 'alias': 'B'}, {'table': 'PIMSCS.UPNIVEL3', 'alias': 'UP3'}, {'table': 'PIMSCS.SAFRUPNIV3', 'alias': 'C'}, {'table': 'PIMSCS.VARIEDADES', 'alias': 'D'}, {'table': 'PIMSCS.TIPO_MATURAC', 'alias': 'E'}, {'table': 'PIMSCS.UPNIVEL1', 'alias': 'F'}, {'table': 'PIMSCS.FORNECS', 'alias': 'G'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.SAFRUPNIV3', 'alias': 'D'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': 'OBJ2'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.HISTPREPRO', 'alias': 'OBJ3'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.QUEIMA_HE', 'alias': 'QH'}, {'table': 'PIMSCS.QUEIMA_DE', 'alias': 'QD'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.HISTPREPRO', 'alias': 'A'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.HISTPREPRO', 'alias': 'A2'}, {'table': 'PIMSCS.UPNIVEL3', 'alias': 'A'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.SAFRUPNIV3', 'alias': 'B2'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': 'OBJ'}, {'table': 'PIMSCS.ESTAGIOS', 'alias': 'B'}, {'table': 'PIMSCS.UPNIVEL3', 'alias': 'UP3'}, {'table': 'PIMSCS.SAFRUPNIV3', 'alias': 'C'}, {'table': 'PIMSCS.VARIEDADES', 'alias': 'D'}, {'table': 'PIMSCS.TIPO_MATURAC', 'alias': 'E'}, {'table': 'PIMSCS.UPNIVEL1', 'alias': 'F'}, {'table': 'PIMSCS.FORNECS', 'alias': 'G'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.SAFRUPNIV3', 'alias': 'D'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': 'OBJ2'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.HISTPREPRO', 'alias': 'OBJ3'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.OCORTEMD_DE', 'alias': 'A'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.HISTPREPRO', 'alias': 'A'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.HISTPREPRO', 'alias': 'A2'}, {'table': 'PIMSCS.UPNIVEL3', 'alias': 'A'}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.HISTPREPRO', 'alias': None}, {'table': 'PIMSCS.SAFRUPNIV3', 'alias': 'B2'}]

How to extract table names and column names from sql query?

Really, this is no easy task. You could use a lexer (ply in this example) and define several rules to get several tokens out of a string. The following code defines these rules for the different parts of your SQL string and puts them back together as there could be aliases in the input string. As a result, you get a dictionary (result) with the different tablenames as key.

import ply.lex as lex, re

tokens = (
    "TABLE",
    "JOIN",
    "COLUMN",
    "TRASH"
)

tables = {"tables": {}, "alias": {}}
columns = []

t_TRASH = r"Select|on|=|;|\s+|,|\t|\r"

def t_TABLE(t):
    r"from\s(\w+)\sas\s(\w+)"

    regex = re.compile(t_TABLE.__doc__)
    m = regex.search(t.value)
    if m is not None:
        tbl = m.group(1)
        alias = m.group(2)
        tables["tables"][tbl] = ""
        tables["alias"][alias] = tbl

    return t

def t_JOIN(t):
    r"inner\s+join\s+(\w+)\s+as\s+(\w+)"

    regex = re.compile(t_JOIN.__doc__)
    m = regex.search(t.value)
    if m is not None:
        tbl = m.group(1)
        alias = m.group(2)
        tables["tables"][tbl] = ""
        tables["alias"][alias] = tbl
    return t

def t_COLUMN(t):
    r"(\w+\.\w+)"

    regex = re.compile(t_COLUMN.__doc__)
    m = regex.search(t.value)
    if m is not None:
        t.value = m.group(1)
        columns.append(t.value)
    return t

def t_error(t):
    raise TypeError("Unknown text '%s'" % (t.value,))
    t.lexer.skip(len(t.value))

# here is where the magic starts
def mylex(inp):
    lexer = lex.lex()
    lexer.input(inp)

    for token in lexer:
        pass

    result = {}
    for col in columns:
        tbl, c = col.split('.')
        if tbl in tables["alias"].keys():
            key = tables["alias"][tbl]
        else:
            key = tbl

        if key in result:
            result[key].append(c)
        else:
            result[key] = list()
            result[key].append(c)

    print result
    # {'tb1': ['col1', 'col7'], 'tb2': ['col2', 'col8']}    

string = "Select a.col1, b.col2 from tb1 as a inner join tb2 as b on tb1.col7 = tb2.col8;"
mylex(string)

How can I get column names from a table in Oracle?

You can query the USER_TAB_COLUMNS table for table column metadata.

SELECT table_name, column_name, data_type, data_length
FROM USER_TAB_COLUMNS
WHERE table_name = 'MYTABLE'

Get Table Name That Contains A Specific Keyword

You Can Do Like This

$query1 = mysqli_query($your_connection_to_db, "SHOW TABLES FROM movie_tags");

while ($array = mysqli_fetch_array($query1)){
    $query2 = mysqli_query($your_connection_to_db, "SELECT * FROM `".$array[0]."` WHERE id = '57'");
    $rows = mysqli_num_rows($query2);

    if($rows>0){
        //you can do your code here with $array[0]. Examplebr>        echo "your ".$array[0]." table has 57 in it's id column";
    }
}

Get the table name(s) from MySQL database where column name is like X value is equal to Y

Thanks to l.g.karolos I was able to get what I wanted. Here is the code :

DELIMITER $$

DROP PROCEDURE IF EXISTS getStudentFromClassroom$$
CREATE PROCEDURE getStudentFromClassroom(student_name VARCHAR(255))
BEGIN
  DECLARE done INT DEFAULT FALSE;

  DECLARE _tablename VARCHAR(255);
  DECLARE _columnname VARCHAR(255) DEFAULT 'device';
  DECLARE _columnNameToFind VARCHAR(255) ;

   DECLARE cur1 CURSOR FOR SELECT 
                             CONCAT(TABLE_SCHEMA, '.', TABLE_NAME) AS table_name,
                            COLUMN_NAME AS column_name 
                            FROM INFORMATION_SCHEMA.COLUMNS
                            WHERE COLUMN_NAME IN ('YOUR_COLUMN_NAME')
                                AND TABLE_SCHEMA='YOUR_TABLE';
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

  OPEN cur1;

  read_loop: LOOP
    FETCH cur1 INTO _tablename;

    IF done THEN
      LEAVE read_loop;
    END IF;

    SET @s = CONCAT('SELECT @student_number := COUNT(DISTINCT ', _columnname,') ',_tablename,' FROM ', _tablename, ' WHERE ', _columnname,' = \'', student_name,'\'');
    PREPARE stmt FROM @s;
    EXECUTE stmt;
    DEALLOCATE PREPARE stmt;

    SET @s = CONCAT('SELECT @ total_student_number := COUNT(DISTINCT ', _columnname,') ',_tablename,' FROM ', _tablename);
    PREPARE stmt FROM @s;
    EXECUTE stmt;
    DEALLOCATE PREPARE stmt;

    INSERT INTO getStudentResults VALUES (_tablename,@student_number,@total_student_number);

  END LOOP;

  CLOSE cur1;

END$$

With getStudentResults declares as

    CREATE TEMPORARY TABLE IF NOT EXISTS getStudentResults (
   classroom_name VARCHAR(255),
   student_number INT DEFAULT 0,
   total_student_number INT DEFAULT 0
 );

---

Related Topics