Help Center/ Data Warehouse Service/ FAQs/ Top FAQ

Updated on 2025-10-11 GMT+08:00

Top FAQ

Recently, we have collected FAQ about DWS through Intelligent chatbot. You may find answers to your questions on this page.

Syntax Usage

**Table 1** Syntax Usage
Ranking	FAQ	Page URL
1	How do I query the number of bits in a query string? How do I truncate a substring? How do I replace some strings in the returned result? How do I return the first several characters of a string? How do I filter out the header and tail of a string? How do I get the number of bytes of a specified string?	Character Processing Functions and Operators
2	How do I create a partition table? What are the supported table partition types?	CREATE TABLE PARTITION
3	How do I view all schemas? How do I view all tables in a schema?	Schema
4	How do I add a table column? How do I change a data type? How do I add a NOT NULL constraint to a column? How do I set the primary key? How do I alter table attributes?	ALTER TABLE
5	How do I use date functions? How do I use pg_sleep()? How do I perform month subtraction? How do I use functions to change date types?	Time and Date Processing Functions and Operators
6	How do I change distribution columns? How do I change the distribution column to another column? Why does the data in the distribution column cannot be updated, and the message "Distributed key column can't be updated in current version" is displayed?	How Do I Change Distribution Columns
7	How do I manage partitions? How do I add or delete a partition? How do I rename a partition? How do I query data in a partition?	Creating and Managing Partitioned Tables
8	How do I query the number of rows in a partition? How do I merge two partitions?	ALTER TABLE PARTITION
9	How do I call the stored procedure?	CALL
10	How do I create a table? create table like	CREATE TABLE
11	What is the command for authorization? How do I use the grant syntax? How do I grant the rights of a user to other users? How do I grant table permissions to a user? How do I grant database permissions to a user? What are the foreign table permissions?	GRANT
12	How do I use the REPLACE function? How do I use to_timestamp? How do I covert a timestamp to a specified format? How do I use current_timestamp? How do I use to_number?	Type Conversion Functions

Database Management

**Table 2** Database management
Ranking	FAQ	Page URL
1	How do I view table definitions? How do I view the DDL? How do I view the structure of views? How do I querying the size of a database or a table?	Querying the Table and Database Size
2	How do I clearing tablespaces? How do I use the VACUUM FULL syntax? How do I improve the query performance after a large number of adding, deleting, and modifying operations?	VACUUM
3	How do I check whether a user has permissions on the current table? How do I check whether a user has a certain permission on a table?	How Do I View the Table Permissions of a DWS User?
4	How do I query and terminate blocked statements? How do I query active statements? How do I terminate a session? What should I do when lock waiting times out?	Analyzing SQL Statements That Are Being Executed
5	Is there a detailed description for SQL execution plans? How do I view the execution plan? What are the differences between Nested Loop, Hash Join, and Merge Join?	SQL Execution Plan
6	How do I remove the read-only status? What should I do when the database enters the read-only state?	A DWS Cluster Becomes Read-Only and Is Locked and Data Cannot Be Written
7	How do I collect statistics?	ANALYZE \| ANALYSE
8	How do I configure the optimizer? How do I enable or disable nestloop? How do I enable or disable mergejoin? What are the parameters that affect the execution plan?	Optimizer Method Configuration
9	How do I changing the database time zone? How do I change the time zone?	How to Change a Database's Default Time Zone When the Database Time Is Different from the System Time?
10	How do I query function definitions? How do I use the access privilege inquiry functions? How do I query view definitions?	System Information Functions
11	What are the technical specifications? What are the supported partition table sizes? What is the maximum data volume in a single table? What is the maximum number of columns supported by a table?	Technical Specifications
12	What are the developer operations? How do I specify whether to enable the optimizer's use of a distributed framework?	Developer Options

Cluster Management

**Table 3** Cluster management
Ranking	FAQ	Page URL
1	What should I do when disk usage is too high? What should I do if the disk is full? What should I do if the cluster becomes read-only? What should I do if a disk alarm is generated? How do I set the disk threshold? How do I enable disk alarm subscription?	A DWS Cluster Becomes Read-Only and Is Locked and Data Cannot Be Written
2	How do I view basic cluster information? How do I viewing the EIP of a cluster? How do I viewing the database connection address? What are the cluster flavors? What is the basic disk information?	Viewing Cluster Details
3	How do I purchase a cluster?	Creating a Cluster
4	What should I do if the cluster is unbalanced? How do I perform primary/standby cluster switchover?	Performing a Primary/Standby Switchback