Looking for JDBC SQL code to fetch default column names from table which has list of columns. is there any SQL command or query to fetch default column names from table.
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hello "I m new to Hbase.. My question is How to create a table in hbase with column family & column names inside the columnfamily without passing values and row key?Is it possible to create that table in hbase shell?
In Sql we create a table first and later we add data ..same thing how can we do it in hbase?
HBase is a nosql key value database. The tables can be created just by specifying table name and column family for example create "sampletable","m" where sampletable is table name and m is column family. If you want to use SQL queries on HBase try Apache Phoenix.
I am writing pl/sql code with dynamic sql statements to ALTER TABLE on table B when new columns are found in table A. When I query all_tab_columns from table a I can return all I need to do this, but in some cases it throws an error when I specify a length for the new column in table B (for example, DATE which I expected). So, I need to parse the results from all_tab_columns to include or exclude a length in the ALTER TABLE statement. On which data types should I leave off a length specification?
I have two columns Id and Name in Hive table, and I want to delete the Name column. I have used following command:
ALTER TABLE TableName REPLACE COLUMNS(id string);
The result was that the Name column values were assigned to the Id column.
How can I drop a specific column of the table and is there any other command in Hive to achieve my goal?
In addition to the existing answers to the question : Alter hive table add or drop column
As per Hive documentation,
REPLACE COLUMNS removes all existing columns and adds the new set of columns.
REPLACE COLUMNS can also be used to drop columns. For example, ALTER TABLE test_change REPLACE COLUMNS (a int, b int); will remove column c from test_change's schema.
The query you are using is right. But this will modify only schema i.e, the metastore. This will not modify anything on data side.
So, before you are dropping the column you should make sure that you hav correct data file.
In your case the data file should not contain name values.
If you don't want to modify the file then create another table with only specific column that you need.
Create table tablename as select id from already_existing_table
let me know if this helps.
Is there any query that can be used to retrive the Tables and its column attributes like column name , datatype, nullable etc for all the tables inside the database
For Oracle Pl/SQL
The Oracle SQL you need would be the following (run as user 'SYS'):
select owner, table_name, column_name, data_type, nullable
from dba_tab_columns;
If you do a desc dba_tab_columns you will get a list of many more columns which may be of interest to you as part of your result set.
You can use a SQL tool (i.e. SQL*Plus) to run this query or you can use PL/SQL to call this query and put the results in PL/SQL variables then print them out via DBMS_OUTPUT.PUT_LINE().
HTH
As part of my project, new columns are introduced in many tables. I wanted to find out the date in which this columns are introduced. Is there a way I can query the date of insertion of all the columns in a specific table in Oracle SQL Developer 3.0.04.
You can try to use the last_ddl_time object from the dba_objects table.