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2019-11-15 FridayLogic: Deductive Logic

Key to solving deductive logic puzzles is coming up with a strategy for identifying and discarding possibilities in a systematic fashion.

Author: Eli Feuerstein [39986-6380482]
I Love LogicNo Comments
Last: No Comments
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2019-11-15 FridaySQL: Miscellaneous concepts

You cannot do aggregates on the results of analytic functions or even use analytic functions in a where clause. You need to do an inline view to perform analytic functions first, then aggregate in the outer query.

Author: Kim Berg Hansen [40027-6399367]
Select from SQLNo Comments
Last: No Comments
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2019-11-15 FridayOracle PL/SQL: Retrieving Session Information with SYS_CONTEXT

SQL statements and anonymous PL/SQL blocks are always run with invoker's rights (AUTHID CURRENT_USER), which means that all currently-enabled roles are used to resolve references to identifiers. PL/SQL program units that are complied with definer's rights (AUTHID DEFINER, the default) can only use privileges granted directly to the schema. Roles are not used.

Author: Steven Feuerstein [40026-6399341]
PL/SQL ChallengeNo Comments
Last: No Comments
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2019-11-15 FridayDatabase Design: Storage Parameters

When you add data to a table, the database allocates storage for it. This space remains allocated when you delete rows.

You can deallocate space above the high water mark with:

alter table <tablename> 
  deallocate unused

Truncate removes all the rows and by default deallocates all storage except the first extent. To remove all allocated space, use:

truncate table <tablename> 
  drop all storage
Author: Chris Saxon [39466-6408661]
Dynamite DB DesignNo Comments
Last: No Comments
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2019-11-15 FridayJava: Lambda

Learn what happens when different types of functional interfaces are used together and how to take advantage of the paradigm.

Author: Rafael Chinelato Del Nero [40046-6408842]
Jump Into JavaNo New Comments
Objections: SUBMITTED
Last: 2019-11-15 15:26:18
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2019-11-08 FridaySQL: MULTISET

Functions MULTISET and COLLECT both can create collections, but MULTISET accepts a SELECT as parameter, while COLLECT is an aggregate function. Both can be useful in different situations.

Author: Kim Berg Hansen [39569-6080243]
Select from SQLNo Comments
Last: No Comments
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2019-11-08 FridayJava: Lambda

Match the correspondent lambda and method reference to each functional interface and learn how to define your functions to perform the action you need. 

Author: Rafael Chinelato Del Nero [39966-6366656]
Jump Into JavaNo New Comments
Objections: SUBMITTED
Last: 2019-11-12 14:26:27
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2019-11-08 FridayDatabase Design: JSON

You can check if a JSON document contains a given attribute with JSON_value or JSON_exists

JSON_value

This searches the specified path, returning the corresponding value. If no matching value is found, this returns null by default. You can change this behaviour with the ON EMPTY clause.

JSON_exists

This searches the specified path, returning true if the value exists and false if it doesn't.

Author: Chris Saxon [39346-6352128]
Dynamite DB DesignNo Comments
Last: No Comments
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2019-11-08 FridayOracle PL/SQL: Error Management

When you run an anonymous block, the PL/SQL engine will first of all parse and compile the block. If all goes well, then the PL/SQL runtime engine will execute the compiled code. If, however, your code fails to compile, well....you will get a compile error, rather than an runtime exception.

Author: Steven Feuerstein [39886-6278299]
PL/SQL ChallengeNo New Comments
Objections: SUBMITTED
Last: 2019-11-12 11:42:22
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2019-11-08 FridayLogic: Deductive Logic

Key to solving deductive logic puzzles is coming up with a strategy for identifying and discarding possibilities in a systematic fashion.

Author: Eli Feuerstein [39926-6324362]
I Love LogicNo New Comments

Last: 2019-11-11 13:33:27
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2019-11-01 FridayLogic: Deductive Logic

Key to solving deductive logic puzzles is coming up with a strategy for identifying and discarding possibilities in a systematic fashion.

Author: Eli Feuerstein [39846-6260063]
I Love LogicNo Comments
Last: No Comments
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2019-11-01 FridayJava: Lambda

Absorb the powerful concepts of functional programming with lambdas by solving this Java quiz!

Author: Rafael Chinelato Del Nero [39906-6305906]
Jump Into JavaNo Comments
Last: No Comments
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2019-11-01 FridaySQL: Expression Lists

Expression lists in either IN or equality conditions can sometimes be more clear and understandable than using simple equality conditions with a lot of AND and OR and parentheses.

Author: Kim Berg Hansen [39586-6080242]
Select from SQLNo Comments
Last: No Comments
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2019-11-01 FridayDatabase Design: Check Constraints

You can validate the case of letters using the functions UPPER and LOWER or regular expressions.

Author: Chris Saxon [39166-6279704]
Dynamite DB DesignNo Comments
Last: No Comments
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2019-11-01 FridayOracle PL/SQL: Comparing Object Type Instances

If you want to perform object type instance comparison in PL/SQL, you need to create a MAP or ORDER method for the type.

Author: Steven Feuerstein [39806-6214451]
PL/SQL ChallengeNo Comments
Last: No Comments
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2019-10-25 FridayLogic: Deductive Logic

Key to solving deductive logic puzzles is coming up with a strategy for identifying and discarding possibilities in a systematic fashion.

Author: Eli Feuerstein [39766-6196375]
I Love LogicNo Comments
Last: No Comments
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2019-10-25 FridayJava: Lambda

You will learn in details about how functional interfaces work with Java. 

Author: Rafael Chinelato Del Nero [39826-6241800]
Jump Into JavaNo New Comments
Objections: SUBMITTED
Last: 2019-11-12 11:40:46
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2019-10-25 FridaySQL: GROUPING_ID

Function GROUPING_ID is a bitmap that gives you the result of multiple calls to the GROUPING function in a single call.

Author: Kim Berg Hansen [39568-6080241]
Select from SQLNo Comments
Last: No Comments
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2019-10-25 FridayOracle PL/SQL: Packages

tbc

Author: Steven Feuerstein [39726-6169403]
PL/SQL ChallengeNo Comments
Last: No Comments
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2019-10-25 FridayDatabase Design: JSON Indexes

You can search JSON documents using dot-notation to list the path to the attribute. This can use an index with any of the following expressions:

  • The dot-notation path to the attribute
  • JSON_value searching the same path with the RETURNING and ERROR ON ERROR clauses
  • JSON_query matching how the database rewrites the dot-notation expression
Author: Chris Saxon [39046-6160229]
Dynamite DB DesignNo New Comments

Last: 2019-10-27 09:57:45
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2019-10-18 FridayOracle PL/SQL: Querying Data with PL/SQL

If you need to get the number of rows that will be returned by a query before you fetch that data, you could BULK COLLECT into a collection and use the COUNT method. You should only do so for small datasets, however, since the collection will consume PGA memory. You can also use the COUNT-OVER analytic function, but this could cause excessive CPU consumption if you are calling the query from a user interface that allows the user to page through chunks of the dataset.

Author: Steven Feuerstein [39687-6133518]
PL/SQL ChallengeNo Comments
Last: No Comments
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2019-10-18 FridayLogic: Deductive Logic

Key to solving deductive logic puzzles is coming up with a strategy for identifying and discarding possibilities in a systematic fashion.

Author: Eli Feuerstein [39686-6169378]
I Love LogicNo Comments
Last: No Comments
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2019-10-18 FridaySQL: Data Type Comparison Rules

Blank-padded comparison is only used by the database if everything to be compared is CHAR datatype or mix of CHAR and literals. Other cases you need to handle the blank-padding in CHAR columns by implementing your own blank-padded comparison.

Author: Kim Berg Hansen [39567-6080236]
Select from SQLNo Comments
Last: No Comments
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2019-10-18 FridayDatabase Design: Unique Constraints

You can specify an existing index for a unique constraint with the USING INDEX clause.

This index must contain all the columns in the constraint. But they can be in a different order. It can have more columns than the constraint, provided:

  • It is a nonunique index
  • The constraint's columns are the index's leading columns
Author: Chris Saxon [39666-6160226]
Dynamite DB DesignNo Comments
Last: No Comments
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2019-10-18 FridayJava: Method Reference

You will learn how to manipulate Method References when instantiating a new class and will understand better the concept of higher functions and functional programming with Java.

Author: Rafael Chinelato Del Nero [39746-6178380]
Jump Into JavaNo Comments
Last: No Comments
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2019-10-11 FridayDatabase Design: Database constraints

To ensure that at most one row can store the same values in a set of columns, define primary key or unique constraint on them.

To compare values in columns, define a check constraint.

Author: Chris Saxon [38746-6089187]
Dynamite DB DesignNo Comments
Last: No Comments
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2019-10-11 FridaySQL: ADD_MONTHS

Adding YEAR TO MONTH INTERVAL to a DATE can result in invalid dates, but ADD_MONTHS has built-in rules to handle end-of-month issues.

Author: Kim Berg Hansen [39566-6080208]
Select from SQLNo Comments
Last: No Comments
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2019-10-11 FridayJava: Flow Control

You will learn how to use a switch case statement with Java 13 making use of lambdas and the reserved word yield.

Author: Rafael Chinelato Del Nero [39646-6115820]
Jump Into JavaNo Comments
Last: No Comments
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2019-10-11 FridayLogic: Deductive Logic

Key to solving deductive logic puzzles is coming up with a strategy for identifying and discarding possibilities in a systematic fashion.

Author: Eli Feuerstein [39546-6071422]
I Love LogicNo Comments
Last: No Comments
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2019-10-11 FridayOracle PL/SQL: SQL%ROWCOUNT

SQL%ROWCOUNT returns the numbers of rows affected by the most recently executed SQL statement in your PL/SQL context. It is not cumulative within a PL/SQL block.

Author: Steven Feuerstein [39606-6089130]
PL/SQL ChallengeNo Comments
Last: No Comments
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2019-10-04 FridayOracle PL/SQL: REGEXP_REPLACE

When you are asked to remove text from the start or end of a string, look first at regular expression functions, like REGEXP_REPLACE. You can usually get the job done with powerful regular expressions. If that is not an option for you, take a look at the trim functions (LTRIM, RTRIM and TRIM). If they fit your requirements, go for it. But also be ready to use SUBSTR and INSTR to get the job done.

Author: Steven Feuerstein [39506-6027594]
PL/SQL ChallengeNo Comments
Last: No Comments
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2019-10-04 FridaySQL: Object Tables

When you use object types inside relational tables, that type can either be used as the type of a column or the type of the entire table, in which case it is referred to as an object table. In this case, each attribute of the type materializes as a column, and you do not need to use a table alias. If an individual column is an object type, then you must use a table alias to reference attributes in that column.

Author: Steven Feuerstein [39447-5975259]
Select from SQLNo Comments
Last: No Comments
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2019-10-04 FridayDatabase Design: Views

You can insert rows in a view that fail the where clause. So you can add in values you can't query back out again!

To avoid this, add the WITH CHECK OPTION clause. This raises an ORA-01402 when you run DML on the view that produces rows you can't select again.

Author: Chris Saxon [38566-6036319]
Dynamite DB DesignNo Comments
Last: No Comments
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2019-10-04 FridayLogic: Deductive Logic

Key to solving deductive logic puzzles is coming up with a strategy for identifying and discarding possibilities in a systematic fashion.

Author: Eli Feuerstein [39486-6010000]
I Love LogicNo Comments
Last: No Comments
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2019-09-27 FridayOracle PL/SQL: Boolean Expressions

Boolean expressions can be used directly where a boolean argument is expected or in assignment to a boolean variable.

Author: Kim Berg Hansen [38786-5496218]
PL/SQL ChallengeNo Comments
Last: No Comments
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2019-09-27 FridayLogic: Deductive Logic

Key to solving deductive logic puzzles is coming up with a strategy for identifying and discarding possibilities in a systematic fashion.

Author: Eli Feuerstein [39446-5948959]
I Love LogicNo Comments
Last: No Comments
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2019-09-27 FridaySQL: JSON_EQUAL

Added in Oracle Database 18c, you can compare two JSON documents with JSON_equal. This returns true if the documents are the same according to the JSON standard.

This ignores insignificant whitespace and attribute order.

Author: Chris Saxon [39286-5854667]
Select from SQLNo Comments
Last: No Comments
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2019-09-27 FridayDatabase Design: Check Constraints

If a check constraint references multiple columns, it cannot be created inline on a specific column, but must be specified out-of-line on the table.

Author: Kim Berg Hansen [38927-5854637]
Dynamite DB DesignNo Comments
Last: No Comments
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2019-09-20 FridayDatabase Design: Partitioning

Starting in Oracle Database 12.2, you can create partitioned external tables. Each partition points to its own set of files.

This supports list and range partitioning and subpartitioning.

 

Author: Chris Saxon [39246-5854632]
Dynamite DB DesignNo New Comments

Last: 2019-09-25 15:40:32
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2019-09-20 FridayLogic: Deductive Logic

Key to solving deductive logic puzzles is coming up with a strategy for identifying and discarding possibilities in a systematic fashion.

Author: Eli Feuerstein [39386-5888614]
I Love LogicNo Comments
Last: No Comments
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2019-09-20 FridayOracle PL/SQL: Non-Instantiable Object Types

When a type is declared NOT INSTANTIABLE, you cannot initialize a variable based on the food_ot type (ie, with its constructor). It is still possible, however, to declare a variable using that type and then instantiate and use it, via a subtype constructor.

Author: Steven Feuerstein [39406-5905848]
PL/SQL ChallengeNo Comments
Last: No Comments
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2019-09-20 FridaySQL: TRUNC

TRUNC on a DATE column accepts multiple format models for the same truncation. Beware the differences between formats like D, DD and DDD.

Author: Kim Berg Hansen [39207-5770418]
Select from SQLNo Comments
Last: No Comments
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2019-09-20 FridayJava: Threads and Locks

You will learn how to use CompletableFuture asynchronously with two Threads. 

Author: Rafael Chinelato Del Nero [39426-5931618]
Jump Into JavaNo New Comments
Objections: SUBMITTED
Last: 2019-09-27 12:59:33
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2019-09-13 FridayOracle PL/SQL: Passing Actuals with Named Notation

You can use named notation virtually anywhere and in any way you can invoke a piece of executable PL/SQL code, from procedures to functions (from within a SQL statement and natively in a PL/SQL block), to object type methods. And starting with Oracle Database 18c, you can even used named notation in calls to qualified expressions (kinda like type constructors) for record and collection types!

Author: Steven Feuerstein [39326-5854775]
PL/SQL ChallengeNo Comments
Last: No Comments
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2019-09-13 FridayJava: Streams

You will learn how to manipulate Stream that might be null in a safe way.

Author: Rafael Chinelato Del Nero [39366-5863257]
Jump Into JavaNo Comments
Last: No Comments
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2019-09-13 FridayLogic: Deductive Logic

Key to solving deductive logic puzzles is coming up with a strategy for identifying and discarding possibilities in a systematic fashion.

Author: Eli Feuerstein [39306-5837597]
I Love LogicNo Comments
Last: No Comments
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2019-09-13 FridaySQL: Lateral inline view

LATERAL can sometimes let you create a single collated inline view to replace multiple scalar subqueries to retrieve multiple columns instead of just a single column.

Author: Kim Berg Hansen [39226-5770404]
Select from SQLNo Comments
Last: No Comments
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2019-09-13 FridayDatabase Design: Primary Keys

The USING INDEX clause allows you to define which index a primary key will use. This can be the name of an existing index. Or a complete CREATE INDEX statement defining a new one.

Author: Chris Saxon [38506-5854630]
Dynamite DB DesignNo Comments
Last: No Comments
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2019-09-06 FridayOracle PL/SQL: Object Type Hierarchies

When you build hierarchies of object types, remember that attributes of parents are passed down to the subtypes. So when you call a default constructor function for a subtype, you must include a value for all the attributes in the parent(s) as well.

Author: Steven Feuerstein [39208-5770457]
PL/SQL ChallengeNo New Comments

Last: 2019-09-07 14:49:40
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2019-09-06 FridaySQL: Xquery functions

Retrieving information from XML data can sometimes profitably be done by using Xquery functions like fn:count along with suitable Xpath/Xquery expressions.

Author: Kim Berg Hansen [39206-5770395]
Select from SQLNo Comments
Last: No Comments
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