Updated on 2023-11-14 GMT+08:00

Inserting Data to a Table

A new table contains no data. You need to insert data to the table before using it. This section describes how to insert a row or multiple rows of data from a specified table using INSERT. If a large amount of data needs to be imported to a table in batches, see Import Methods.

Background

The length of a character on the server and client may vary by the used character sets. A string entered on the client will be processed based on the server's character set, so the output may differ from the input.

Table 1 Comparison of character set output between the client and server

Procedure

Same Character Sets

Different Character Sets

No operations are performed on the string while it is saved and read.

Your expected result is returned.

If the character sets for input and output on the client are the same, your expected result is returned.

Operations (such as executing string functions) are performed to the string while it is saved and read.

Your expected result is returned.

The result may differ from expected, depending on the operations performed on the string.

A long string is truncated while it is saved.

Your expected result is returned.

If the character sets used on the client and server are different in character length, an unexpected result may occur.

More than one of the preceding operations can be performed on a string. For example, if the character sets of the client and server are different, a string may be processed and then truncated. In this case, the result will also be unexpected. For details, see Table 2.

Long strings are truncated only if DBCOMPATIBILITY is set to TD (compatible with Teradata) and td_compatible_truncation is set to on.

Run the following statements to create tables table1 and table2 to be used in the examples:

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CREATE TABLE table1(id int, a char(6), b varchar(6),c varchar(6)) ;
CREATE TABLE table2(id int, a char(20), b varchar(20),c varchar(20)) ;
Table 2 Examples

ID

Server Character Set

Client Character Set

Automatic Truncation Enabled

Examples

Result

Description

1

SQL_ASCII

UTF8

Yes

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INSERT INTO table1 VALUES(1,reverse('123AA78'),reverse('123AA78'),reverse('123AA78'));
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3
id |a|b|c
----+------+------+------
1 | 87| 87| 87

A string is reversed on the server and then truncated. Because character sets used by the server and client are different, character A is displayed in multiple bytes on the server and the result is incorrect.

2

SQL_ASCII

UTF8

Yes

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INSERT INTO table1 VALUES(2,reverse('123A78'),reverse('123A78'),reverse('123A78'));
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3
id |a|b|c
----+------+------+------
2 | 873| 873| 873

A string is reversed and then automatically truncated. Therefore, the result is unexpected.

3

SQL_ASCII

UTF8

Yes

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INSERT INTO table1 VALUES(3,'87A123','87A123','87A123'
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3
id |   a   |   b   |   c
----+-------+-------+-------
  3 | 87A1 | 87A1 | 87A1

The column length in the string type is an integer multiple of the length in client character encoding. Therefore, the result is correct after truncation.

4

SQL_ASCII

UTF8

No

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INSERT INTO table2 VALUES(1,reverse('123AA78'),reverse('123AA78'),reverse('123AA78'));
INSERT INTO table2 VALUES(2,reverse('123A78'),reverse('123A78'),reverse('123A78'));
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3
4
id |a|b|c
----+-------------------+--------+--------
1 | 87 321| 87 321 | 87 321
2 | 87321| 87321| 87321

Similar to the first example, multi-byte characters no longer indicate the original characters after being reversed.

Common Operations

You need to create a table before inserting data to it. For details about how to create a table, see Creating and Managing Tables.

  • Insert a row to table customer_t1:
    Data values are arranged in the same order as the columns in the table and are separated by commas (,). Generally, they are text values (constants). Scalar expressions are also allowed.
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    INSERT INTO customer_t1(c_customer_sk, c_customer_id, c_first_name) VALUES (3769, 'hello', 'Grace');
    
    If you know the sequence of the columns in the table, you can obtain the same result without listing these columns. For example, the following statement generates the same result as the preceding statement:
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    INSERT INTO customer_t1 VALUES (3769, 'hello', 'Grace');
    
    If you do not know some of the values, you can omit them. If no value is specified for a column, the column is set to the default value. The following shows an example.
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    INSERT INTO customer_t1 (c_customer_sk, c_first_name) VALUES (3769, 'Grace');
    
    INSERT INTO customer_t1 VALUES (3769, 'hello');
    
    You can also specify the default value of a column or row:
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    INSERT INTO customer_t1 (c_customer_sk, c_customer_id, c_first_name) VALUES (3769, 'hello', DEFAULT);
    
    INSERT INTO customer_t1 DEFAULT VALUES;
    
  • To insert multiple rows, run the following statement:
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    INSERT INTO customer_t1 (c_customer_sk, c_customer_id, c_first_name) VALUES 
        (6885, 'maps', 'Joes'),
        (4321, 'tpcds', 'Lily'),
        (9527, 'world', 'James');
    

    You can also insert multiple rows by running the statement for inserting one row for multiple times. However, you are advised to run this command to improve efficiency.

  • Insert data to a table from a specified table. For example, run the following statement to insert the data of table customer_t1 to the backup table customer_t2.
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    CREATE TABLE customer_t2
    (
        c_customer_sk             integer,
        c_customer_id             char(5),
        c_first_name              char(6),
        c_last_name               char(8)
    ) ;
    
    INSERT INTO customer_t2 SELECT * FROM customer_t1;
    

    If there is no implicit conversion between the data types of the specified table and those of the current table, the two tables must have the same data types when data is inserted from the specified table to the current table.

  • Delete a backup table.
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    DROP TABLE customer_t2 CASCADE;
    

    If the table to be deleted is associated with other tables, delete the associated tables first.