PostgreSQL Server General Question and Answer.

    

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1.      What Is Maximum Size Of Table In PostgreSQL? 

1.      The PostgreSQL Has Maximum Size of Table Is 32TB.

            2.      How To Rename A Table In PostgreSQL

1.      Alter Table Events Rename To Events_Backup;

3.      How To Truncate A Table In PostgreSQL

1.      Truncate My_Table

2.      Truncate My_Table Restart Identity

4.      How To Duplicate A Table In PostgreSQL

1.      Create Table Dupe_Users As (Select * From Users);

2.      Create Table Dupe_Users As (Select * From Users) With No Data; (-- The `With No Data` Here Means Structure Only, No Actual Rows)

5.      How To Add A Column In PostgreSQL

1.      Alter Table Users Add Column Created_At Timestamp Without Time Zone;

2.      Alter Table Users Add Column Bio Character Varying Not Null;

3.      Alter Table Users Add Column Active Boolean Default True;

6.      How To Drop A Column In PostgreSQL

1.      Alter Table Users Drop Column Created_At;

7.      How To Rename A Column In PostgreSQL

1.      Alter Table Users Rename Column Registered_At To Created_At;

            8.      How To Add A Default Value To A Column In PostgreSQL

1.      Alter Table Orders Alter Column Total_Cents Set Default 0; (-- Example: Orders Have A Default Total Of 0 Cents)

2.      Alter Table Items Alter Column Available Set Default True; (-- Example: Items Are Available By Default)

9.      How To Remove A Default Value From A Column In PostgreSQL

1.      Alter Table Orders Alter Column Total_Cents Drop Default;

10.  How To Add A Not Null Constraint In PostgreSQL

1.      Alter Table Users Alter Column Email Set Not Null;

11.  How To Remove A Not Null Constraint In PostgreSQL

1.      Alter Table Users Alter Column Email Drop Not Null;

12.  How To Create An Index In PostgreSQL

1.      Create Index Concurrently "Index_Created_At_On_Users" On Users Using Btree (Created_At);

2.      Create Index Concurrently "Index_User_Id_And_Time_On_Events" On Events Using Btree (User_Id, Time);

3.      Create Unique Index Concurrently "Index_Stripe_Event_Id_On_Stripe_Events"On Stripe_Events Using Btree(Stripe_Event_Id);

4.      Create Index Concurrently "Index_Active_Users" On Users Using Btree(Created_At) Where Active Is True;

5.      Create Unique Index Concurrently "Index_Active_Credit_Cards" On Credit_Cards Using Btree(User_Id) Where Active Is True;

             13.  How To Drop An Index In PostgreSQL

1.      Drop Index Index_Created_At_On_Users;