alter cmds in sql

Author: mayankSystems

src/main/java/dev/mayankg/db_concepts/mysql/exc02/sql_alter_cmds.sql

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+-- Add a new column 'phone' to companies table
+ALTER TABLE companies
+ADD COLUMN phone VARCHAR(15);
+
+-- Add a NOT NULL column 'employee_count' with a default value
+ALTER TABLE companies
+ADD COLUMN employee_count INT NOT NULL DEFAULT 1;
+
+-- Remove the 'phone' column from companies
+ALTER TABLE companies
+DROP COLUMN phone;
+
+-- Rename the 'companies' table to 'suppliers'
+RENAME TABLE companies TO suppliers;
+
+-- Rename it back to 'companies'
+ALTER TABLE suppliers RENAME TO companies;
+
+-- Rename column 'name' to 'company_name'
+ALTER TABLE companies
+RENAME COLUMN name TO company_name;
+
+-- Modify column 'company_name' to have a new default value and length
+ALTER TABLE companies
+MODIFY company_name VARCHAR(100) DEFAULT 'unknown';
+
+-- Rename column 'business' to 'biz_name' and change its data type
+ALTER TABLE suppliers
+CHANGE business biz_name VARCHAR(50);
+
+-- Add a CHECK constraint to ensure purchase_price is non-negative
+ALTER TABLE houses 
+ADD CONSTRAINT positive_pprice CHECK (purchase_price >= 0);
+
+-- Drop the CHECK constraint named 'positive_pprice'
+ALTER TABLE houses 
+DROP CONSTRAINT positive_pprice;