Add LOCK statement wiki.

wiki/LOCK.md

@@ -0,0 +1,45 @@
+
+LOCK statement obtains a table-level lock, waiting if necessary for any conflicting locks to be released.
+More about LOCK statement in PostgreSQL: https://www.postgresql.org/docs/11/sql-lock.html  
+
+Following clauses are supported:
+- IN(mode) - mode specifies which locks this lock conflicts with.  
+Mode can be: 
+    - jet.LOCK_ACCESS_SHARE          
+    - jet.LOCK_ROW_SHARE             
+    - jet.LOCK_ROW_EXCLUSIVE         
+    - jet.LOCK_SHARE_UPDATE_EXCLUSIVE
+    - jet.LOCK_SHARE                 
+    - jet.LOCK_SHARE_ROW_EXCLUSIVE   
+    - jet.LOCK_EXCLUSIVE             
+    - jet.LOCK_ACCESS_EXCLUSIVE      
+- NOWAIT() - locked table should not wait for any conflicting locks to be released. If the specified lock(s) 
+cannot be acquired immediately without waiting, the transaction is aborted.
+
+## Example
+
+
+```
+lockStmt := Address.
+        LOCK().
+        IN(jet.LOCK_ACCESS_SHARE).
+        NOWAIT()
+```
+
+Debug SQL of above statement:
+
+```sql
+LOCK TABLE dvds.address IN ACCESS SHARE MODE NOWAIT;
+```
+
+### Execute statement
+
+To execute update statement and get sql.Result:
+
+```
+res, err := lockStmt.Exec(db)
+```
+
+Use `ExecContext` to provide context object to execution.
+
+ 

wiki/SELECT.md

@@ -124,14 +124,26 @@ OFFSET 11
 ```
 
 ##### 9. FOR clause 
+
+Lock mode can be:
+- jet.UPDATE()       
+- jet.NO_KEY_UPDATE()
+- jet.SHARE()      
+- jet.KEY_SHARE()    
+
+Lock mode has following clauses:
+- NOWAIT()
+- SKIP_LOCKED()
+
 ```
 Go:
-.FOR(jet.NO_KEY_UPDATE)
+.FOR(jet.NO_KEY_UPDATE().SKIP_LOCKED())
 
 SQL:
-FOR NO KEY UPDATE
+FOR NO KEY UPDATE SKIP LOCKED
 ```
 
+
 ### Two forms of select statements in Jet
 
 #### 1. Classical select statement

wiki/_Sidebar.md

@@ -1,6 +1,7 @@
 
 * [Installation](https://github.com/go-jet/jet/wiki/Installation)
 * [Generator](https://github.com/go-jet/jet/wiki/Generator)
+* [Model data](https://github.com/go-jet/jet/wiki/Model-data.md)
 * [Writing SQL in Go]() 
     * [Expressions](https://github.com/go-jet/jet/wiki/Expressions)
     * [Statements](https://github.com/go-jet/jet/wiki/Statements)
@@ -9,3 +10,4 @@
         * [UPDATE](https://github.com/go-jet/jet/wiki/UPDATE)
         * [DELETE](https://github.com/go-jet/jet/wiki/DELETE)
         * [LOCK](https://github.com/go-jet/jet/wiki/LOCK)
+* [Execution]()