12/19/2023 0 Comments Mysql add column uniqueFortunately, you can get this information from the columns table of the information_schema database as the following query: SELECT IF( count(*) = 1, 'Exist', 'Not Exist') AS result FROM However, there is no statement like ADD COLUMN IF NOT EXISTS available. In some situations, you want to check whether a column already exists in a table before adding it. However, with a big table with hundred of columns, it is more difficult. Duplicate column name 'vendor_group' Code language: SQL (Structured Query Language) ( sql )įor the table with a few columns, it is easy to see which columns are already there. MySQL issued an error message: Error Code: 1060. For example, if you execute the following statement: ALTER TABLE vendors If you accidentally add a column that already exists in the table, MySQL will issue an error. And the hourly_rate column is populated with 0.00 values. The email column is populated with blank values, not the NULL values. Vendors Code language: SQL (Structured Query Language) ( sql ) SELECT id, name, phone, vendor_group, email, hourly_rate Let’s check the data in the vendors table. In such cases, MySQL will use default values for those new columns. Note that both email and hourly_rate columns are assigned to NOT NULL values However, the vendors table already has data. ALTER TABLE vendorsĪDD COLUMN hourly_rate decimal( 10, 2) NOT NULL Code language: SQL (Structured Query Language) ( sql ) SELECT id, name, phone,vendor_groupįourth, add two more columns email and hourly_rate to the vendors table at the same time. We can query the data of the vendors table to see the changes. VALUES( 'Microsoft', '(408)-298-2988', 1) Code language: SQL (Structured Query Language) ( sql ) INSERT INTO vendors( name,phone,vendor_group) Let’s insert some rows into the vendors table. ALTER TABLE vendorsĪDD COLUMN vendor_group INT NOT NULL Code language: SQL (Structured Query Language) ( sql ) At this time, we don’t specify the new column’s position so MySQL adds the vendor_group column as the last column of the vendors table. Third, we add a new column named vendor_group to the vendors table. ALTER TABLE vendorsĪDD COLUMN phone VARCHAR( 15) AFTER name Because we specify the position of the phone column explicitly after the name column, MySQL will obey this. Second, we add a new column named phone to the vendors table. ) Code language: SQL (Structured Query Language) ( sql ) MySQL ADD COLUMN examplesįirst, we create a table named vendors for the demonstration purpose using the following statement: CREATE TABLE IF NOT EXISTS vendors ( Let’s take a look some examples of adding a new column to an existing table. To add two or more columns to a table at the same time, you use the following syntax: ALTER TABLE table ADD column_name_1 column_1_definition ,ĪDD column_name_2 column_2_definition ,Ĭode language: SQL (Structured Query Language) ( sql ) If you don’t explicitly specify the position of the new column, MySQL will add it as the last column. It also allows you to add the new column after an existing column using the AFTER existing_column clause. Third, MySQL allows you to add the new column as the first column of the table by specifying the FIRST keyword.Note that COLUMN keyword is optional so you can omit it. Second, you put the new column and its definition after the ADD COLUMN clause.First, you specify the table name after the ALTER TABLE clause.Let’s examine the statement in more detail. To add a new column to an existing table, you use the ALTER TABLE ADD COLUMN statement as follows: ALTER TABLE table ADD column_name column_definition Code language: SQL (Structured Query Language) ( sql ) Introduction to MySQL ADD COLUMN statement Summary: in this tutorial, we will show you how to add a column to a table using MySQL ADD COLUMN statement.
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