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WHAT IS SQL (STRUCTURED QUERY LANGUAGE) ?<\/span><\/span><\/p>\n SQL is not a programming language like C, JAVA, C ++ .<\/span> ORACLE is a sub language used in databases such as MYSQL , SQL SERVER .<\/span> SQL is a query language used to add , delete , access and update data in a database .<\/span><\/p>\n USAGE AREAS OF SQL<\/span><\/span><\/p>\n Creating , modifying database objects ,<\/span><\/p>\n<\/li>\n Controlling access to database, objects ,<\/span><\/p>\n<\/li>\n Modeling , managing data sets ,<\/span><\/p>\n<\/li>\n Data query , add , delete operations are performed .<\/span><\/p>\n<\/li>\n<\/ul>\n WHY CHOOSE SQL?<\/span><\/span><\/p>\n Allows users to define and modify data .<\/span><\/p>\n<\/li>\n Allows users to set permissions on tables , views .<\/span><\/p>\n<\/li>\n Allows users to access data from relational database management systems .<\/span><\/p>\n<\/li>\n Allows modules to be embedded in different languages .<\/span><\/p>\n<\/li>\n Security, performance , data recovery features are the main features that are effective in choosing sql .<\/span><\/span><\/span><\/p>\n<\/li>\n Provides quick processing of data and easy querying .<\/span><\/span><\/span><\/p>\n<\/li>\n<\/ul>\n CLASSIFICATION OF SQL COMMANDS<\/span><\/span><\/p>\n SQL commands are divided into 3 sections according to their functions :<\/span><\/p>\n DML (Data Manipulation Language) : <\/span><\/span>Data processing language .<\/span><\/span> For managing data with in table or schema objects <\/span>(SELECT , UPDATE , INSERT , MERGE , DELETE , CALL)<\/span><\/span><\/p>\n<\/li>\n D<\/span><\/span>C<\/span><\/span>L (Data <\/span><\/span>Control<\/span><\/span> Language) : Data control language . Used to set authorization or privileges . <\/span><\/span>(<\/span><\/span>GRANT,REVOKE)<\/span><\/span><\/p>\n<\/li>\n D<\/span><\/span>D<\/span><\/span>L (Data <\/span><\/span>Definition<\/span><\/span> Language) : Data definition language . Used to define tables, database structures, or schemas . <\/span><\/span>(CREATE , TRUNCATE , ALTER , COMMENT , DROP , RENAME)<\/span><\/span><\/p>\n<\/li>\n TCL (Transaction Control) : The process is the control language . For managing changes made by DML . <\/span><\/span>(<\/span><\/span>COMMIT , SAVEPOINT , ROLLBACK)<\/span><\/span><\/p>\n<\/li>\n<\/ul>\n SQL WRITING RULES<\/span><\/span><\/span> <\/span><\/p>\n SQL statements do not distinguish between upper and lower case .<\/span><\/p>\n<\/li>\n Keywords cannot be abbreviated or divided into lines<\/span><\/span> (keywords : Select , From , etc.) . <\/span><\/p>\n<\/li>\n Expressions are usually in separate lines . <\/span><\/p>\n<\/li>\n Typically , key expressions are written in capital letters . <\/span><\/p>\n<\/li>\n Date and character type data is written to the left and numeric data is written adjacent to the right . <\/span><\/p>\n<\/li>\n<\/ul>\n CREATING A SQL TABLE<\/span><\/span><\/span><\/p>\n <\/p>\n In the picture you see above , I added my own worker table and my columns to this table with this query .<\/span><\/span> ADDING COMMENT TO TABLE<\/span><\/span><\/span> <\/i><\/span><\/p>\n We can add comments to tables or columns separately .<\/span><\/span><\/span><\/p>\n<\/li>\n Comments can be queried from the USER_TAB_COMMENTS , USER_COL_COMMENTS views .<\/span><\/p>\n<\/li>\n<\/ul>\n CONSTRAINTS<\/span><\/span><\/span> <\/span><\/span><\/p>\n They prevent deletion of interdependent data . <\/span><\/span><\/p>\n<\/li>\n They prevent incorrect data entry . <\/span><\/span><\/p>\n<\/li>\n They ensure that the data is singular . <\/span><\/span><\/p>\n<\/li>\n They can be at the table or column level . <\/span><\/span><\/p>\n<\/li>\n<\/ul>\n NOT NULL CONSTRAINT<\/span><\/span><\/p>\n Prevents specified columns from being NULL . <\/span><\/span><\/p>\n<\/li>\n<\/ul>\n <\/p>\n UNIQUE CONSTRAINT<\/span><\/span><\/p>\n They can be used for one or more columns .<\/span><\/span><\/span><\/span><\/p>\n<\/li>\n You can use more than one unique constraint in a table .<\/span><\/span><\/span><\/span><\/p>\n<\/li>\n<\/ul>\n <\/p>\n PRIMARY KEY CONSTRAINT<\/span><\/span><\/p>\n A primary key can be set for a column . <\/span><\/span><\/p>\n<\/li>\n There can only be one primary key in the table . <\/span><\/span><\/p>\n<\/li>\n The value in this field cannot be NULL . <\/span><\/span><\/p>\n<\/li>\n It also serves as an index . <\/span><\/span><\/p>\n<\/li>\n<\/ul>\n <\/p>\n\n
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CREATE TABLE [schema] table<\/i><\/span>\r\n\r\n (column datatype [DEFAULT expr] [ , .....] );\r\n\r\n<\/i><\/span><\/pre>\nCREATE TABLE ADMIN.ISCI(<\/em>\r\n\r\nEMPLOYEE_ID NUMBER(6),<\/em>\r\n\r\nFIRST_NAME VARCHAR2(20 BYTE),<\/em>\r\n\r\nLAST_NAME VARCHAR2(25 BYTE),<\/em>\r\n\r\nHIRE_DATE DATE,<\/em>\r\n\r\nJOB_ID VARCHAR2(10 BYTE),<\/em>\r\n\r\nSALARY NUMBER(8,2)<\/em>\r\n\r\n)<\/em><\/pre>\n
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COMMENT ON TABLE ADMIN.ISCI 'ADMIN SEMASINDAKI ISCILER' ;<\/em><\/pre>\n
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CREATE TABLE ADMIN.ISCIS(<\/em>\r\n\r\nEMPLOYEE_ID NUMBER(6),<\/em>\r\n\r\nFIRST_NAME VARCHAR2(20 BYTE)NOT NULL,<\/em>\r\n\r\nLAST_NAME VARCHAR2(25 BYTE),<\/em>\r\n\r\nHIRE_DATE DATE,<\/em>\r\n\r\nJOB_ID VARCHAR2(10 BYTE),<\/em>\r\n\r\nSALARY NUMBER(8,2));<\/em><\/pre>\n
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CREATE TABLE ADMIN.ISCIM(<\/em>\r\n\r\nEMPLOYEE_ID NUMBER(6)UNIQUE,<\/em>\r\n\r\nFIRST_NAME VARCHAR2(20 BYTE),<\/em>\r\n\r\nLAST_NAME VARCHAR2(25 BYTE)<\/em>\r\n\r\n);<\/em><\/pre>\n
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CREATE TABLE ADMIN.ISCIZ(<\/em>\r\n\r\nEMPLOYEE_ID NUMBER(6)CONSTRAINT E_PK PRIMARY KEY,<\/em>\r\n\r\nFIRST_NAME VARCHAR2(20 BYTE),<\/em>\r\n\r\nLAST_NAME\u00a0 VARCHAR2(25 BYTE)<\/em>\r\n\r\n);<\/em><\/pre>\n