- Does @transactional lock table?
- Can we write if else in SQL query?
- What is the difference between truncate and delete?
- Why drop table if exists?
- Why truncate is DDL?
- Does Start transaction lock table?
- How do I delete a function in SQL Server?
- Can we use and in case statement in SQL?
- What is difference between drop and delete in SQL?
- Can we truncate database?
- Which of the following SQL clauses is used to delete?
- How can I delete two table data in one query?
- Does a select statement lock a table?
- How do you write a delete statement in SQL?
- What is drop SQL?
- How do I create an if statement in SQL query?
- Why use truncate instead of delete?
- How can I delete duplicate rows in SQL query?
- Will delete statement lock the table?
- How do I do an if statement in SQL?
- Which is faster truncate or drop?
Does @transactional lock table?
LOCK IN SHARE MODE inside a transaction, as you said, since normally SELECTs, no matter whether they are in a transaction or not, will not lock a table..
Can we write if else in SQL query?
In MS SQL, IF…ELSE is a type of Conditional statement. Any T-SQL statement can be executed conditionally using IF… ELSE. If the condition evaluates to True, then T-SQL statements followed by IF keyword will be executed.
What is the difference between truncate and delete?
Delete and truncate both commands can be used to delete data of the table. Delete is a DML command whereas truncate is DDL command. Truncate can be used to delete the entire data of the table without maintaining the integrity of the table.
Why drop table if exists?
The DROP TABLE SQL statement enables you to delete a table from the database. If the table did not exist then attempting to DROP it would cause an error to occur. The DROP TABLE IF EXISTS SQL statement enables a check to see that the table exists prior to attempting the dropping (deletion) of the table.
Why truncate is DDL?
Truncate reinitializes the identity by making changes in data definition therefore it is DDL, whereas Delete only delete the records from the table and doesn’t make any changes in its Definition that’s why it is DML. … Now Truncate Table and Reinsert the records.
Does Start transaction lock table?
If you were to add BEGIN TRANSACTION (or BEGIN TRAN) before the statement it automatically makes the transaction explicit and holds a lock on the table until the transaction is either committed or rolled back.
How do I delete a function in SQL Server?
Right-click the function you want to delete and select Delete. In the Delete Object dialog box, click OK. Click Show Dependencies in the Delete Object dialog box to open the function_nameDependencies dialog box.
Can we use and in case statement in SQL?
CASE can be used in any statement or clause that allows a valid expression. For example, you can use CASE in statements such as SELECT, UPDATE, DELETE and SET, and in clauses such as select_list, IN, WHERE, ORDER BY, and HAVING.
What is difference between drop and delete in SQL?
DELETE is a Data Manipulation Language command, DML command and is used to remove tuples/records from a relation/table. Whereas DROP is a Data Definition Language, DDL command and is used to remove named elements of schema like relations/table, constraints or entire schema. … DELETE is DML.
Can we truncate database?
In order to truncate all tables in your database you must first remove all the foreign key constraints, truncate the tables, and then restore all the constraints. … Load the data for all tables in the database. Execute a cursor to drop all constraints.
Which of the following SQL clauses is used to delete?
3. Which of the following SQL clauses is used to DELETE tuples from a database table? Explanation: The SQL DELETE Query is used to delete the existing records from a table.
How can I delete two table data in one query?
This is the better approach. CREATE TABLE parent ( id INT NOT NULL, PRIMARY KEY (id) ); CREATE TABLE child ( id INT, parent_id INT, FOREIGN KEY (parent_id) REFERENCES parent(id) ON DELETE CASCADE ); You can read more about ON DELETE CASCADE here.
Does a select statement lock a table?
A SELECT in SQL Server will place a shared lock on a table row – and a second SELECT would also require a shared lock, and those are compatible with one another. … The SELECT will not block, and it will not read any “dirty” un-committed data – but it might skip some rows, e.g. not show all your rows in the table.
How do you write a delete statement in SQL?
SQL DELETE StatementDELETE FROM table_name WHERE condition;Example. DELETE FROM Customers WHERE CustomerName=’Alfreds Futterkiste’;DELETE FROM table_name;Example. DELETE FROM Customers;
What is drop SQL?
The SQL DROP TABLE Statement. The DROP TABLE statement is used to drop an existing table in a database.
How do I create an if statement in SQL query?
You can have two choices for this to actually implement:Using IIF, which got introduced from SQL Server 2012: SELECT IIF ( (Obsolete = ‘N’ OR InStock = ‘Y’), 1, 0) AS Saleable, * FROM Product.Using Select Case : SELECT CASE WHEN Obsolete = ‘N’ or InStock = ‘Y’ THEN 1 ELSE 0 END as Saleable, * FROM Product.
Why use truncate instead of delete?
TRUNCATE TABLE is faster and uses fewer system resources than DELETE , because DELETE scans the table to generate a count of rows that were affected then delete the rows one by one and records an entry in the database log for each deleted row, while TRUNCATE TABLE just delete all the rows without providing any …
How can I delete duplicate rows in SQL query?
Delete Duplicates From a Table in SQL ServerFind duplicate rows using GROUP BY clause or ROW_NUMBER() function.Use DELETE statement to remove the duplicate rows.
Will delete statement lock the table?
A delete statement places an exclusive (X) lock on the table. This mean no other query can modify the table’s data until the DELETE transaction completes. You can still read data, but need to use the NOLOCK hint or read uncommitted isolation level.
How do I do an if statement in SQL?
Each IF statement has a condition. If the condition evaluates to TRUE then the statement block in the IF clause is executed. If the condition is FALSE , then the code block in the ELSE clause is executed.
Which is faster truncate or drop?
But TRUNCATE TABLE is faster and uses fewer system and transaction log resources than DELETE. … If you want to remove table definition and its data, use the DROP TABLE statement. You cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint; instead, use DELETE statement without a WHERE clause.